When you are driving on the freeway and following the car in front of you, how close is too close? Let's do an estimation.
1. Pick a car model (preferably the one you drive, but can also be any car of your dream), and find its stopping distance at highway speeds (you can usually find this type of data online).
2. Assuming that the car in front of you suddenly does a hard brake. For simplicity, assume that its braking performance is about the same as yours. Then also assume a reasonable amount of reaction time on your part (the time delay between seeing the brake lights lit up and applying your own brake). In order for you not to run into the car your are following, what's the closest distance you need to keep between the two cars?
3. Redo the same calculation if the vehicle in front of you is a typical big-rig truck. Find its braking data online.
4. There is a rule of thumb which says that you must stay one car length behind the car in front of you for every 10 mi/h of driving speed. From your calculation, does this rule make sense?

Answers

Answer 1

Answer:

1) v= 90km/h  d = 70 m,  2)  x₁ = v t_r,  x₁ = 6.25 m, 3) x₁=6.25 no change

4) x = 22 m

Explanation:

1) for the first part, you are asked to find the minimum safety distance with the vehicle in front

The internet is searched for the stopping distance for two typical speeds on the highway

v (km/ h)      v (m/s)      d (m)

90                  25           70

100                 27.78      84

the safe distance is this distance plus the distance traveled during the person's reaction time, which can be calculated with infirm movement

              v = x / t_r

               x₁ = v t_r

the average reaction time is t_r = 0.25s for a visual stimulus and t_r 0.17 for an auditory stimulus

therefore the safe distance is

              x_total = x₁ + d

2) The distance is the sum of the distance traveled in the reaction

              x₁ = v t_r

for v = 90 km / h

              x₁ = 25 0.25

              x₁ = 6.25 m

for v = 100 km / h

              x₁ = 27.78 0.25

              x₁ = 6.95 m

the total distance is

               x_total = x₁ + d

for v = 90 km / h

             x_total = 25 0.25 + 70

             x_total = 76.25 m

this is the distance until the cars stop and do not collide

3) the stopping distance of a truck is

   v = 90 km / h       d = 100 m

in this case we see that the braking distance is much higher,

the safe distance is given by the distance traveled during the reaction, as the truck brakes slower than the car this distance does not change

4) let's analyze the empirical rule: maintain the length of a car for each increase in speed of v = 10 m / h = 4.47 m / s

for the car case at v = 90km / h = 25 m / s

according to this rule we must this to

           x = 25 / 4.47 = 5.6 cars

each modern car is about 4 m long so the distance is

           x = 22 m

we see that this distance is much greater than the reaction  distance so it does not make much sense


Related Questions

What is the difference in the speed of the generator with a small magnet and a generator with a large magnet?

Answers

With a small magnet with a generator it will be taken up quickly because how small it is while with a big generator it would take more force for it for the generator to attach because the larger the magnet that heavier it will be because it is attached to the North Pole magnet

Answer:

uADHTiszA?kv

Explanation:

What might Earth be like if it had never been hit by the theoretical protoplanet Orpheus?

Answers

Answer:

If Earth hadn't been hit by Orpheus, it would be covered by ocean, with perhaps a few mountaintops emerging through the water. There would be no humans, but there could be other forms of life. Earth would rotate rapidly, as the moon would not be present to produce the tidal friction that slows Earth's rotation today

list the 5 components of fitness

Answers

Yeah what the first person said is the answer you your question

Neuroticism, psychoticism, and extraversion are the three dominant personality traits according to
A. Paul Costa
B. Hans Eysenck
C. Gordon Allport
D. Robert McCrae

Answers

The answer is b I just took the test

Neuroticism, psychoticism, and extraversion are the three dominant personality traits according to Hans Eysenck.

What is Hans Eysenck's theory?

Eysenck's theory of personality is based on three logical attributes namely:  

a) Introversion vs. extroversion Extroversion leads to sociable life , while introversion causes need of being alone and limited interactions

b) Neuroticism vs. stability – Neuroticism leads to anxiousness and an overactive sympathetic nervous system while stability leads to emotional stability.

c) Nsychoticism vs. socialization. - psychoticism  leads to independent thinking, and hostility. While socialization leads to co-operative and conventional behaviour.  

Therefore Neuroticism, psychoticism, and extraversion are the three dominant personality traits according to Hans Eysenck.

To know more about Hans Eysenck's theory follow

https://brainly.com/question/11912668

#SPJ2

Can someone plz explain :
Two cars have the same mass, the first car is moving towards the east and the second is
stationary. If the two cars merge together after a collision and head towards the east their speed
after the collision is equal to.......
A)1/4vi b)1/2vi c)vi d) 2vi

Answers

Answer: Option b, the final velocity is half of the initial velocity.

Explanation:

Here we will use the conservation of the total momentum of a system.

This means that the total momentum at the beginning must be the same as the final momentum.

Where momentum is:

P = M*v

Initially, we have two cars, both with the same mass M, and only one of them has a velocity v.

Then the initial momentum is:

P = M*v + M*0 = M*v

After the collision, the two cars move together. Then the total mass that is moving is equal to the sum of the masses of the cars, this is 2*M

and we can suppose that the two cars move at a final velocity v'

Then the final momentum is:

P' = (2*M)*v'

Now we use the conservation of momentum, then:

P = P'

M*v = (2*M)*v'

Now we need to solve this for v'

(M*v)/(2*M) = v'

v/2 = v'

This means that the final velocity is half of the initial velocity.

Then the correct option is option b.

Why might video games increase creativity while the use of cell phones, the internet, or computers do not?

Answers

Explanation:

Video games are developed around a structure that is unique from your usual media, where there is a sense purpose in mind when playing a game, as decided by the player, and it allows them to explore creative options in order to solve scenarios, depending on the genre. In the use of phones, internet, or computers, this structure is more rare and diverse from video games, which does not lean more toward a creative purpose to build from. That idea gives people the inspiration and discover skills they never knew they even had.

1. What is matter?
2. What are the three phases of matter?
3. Describe how gas particles move.
4. What is temperature?
5. The slower the particles, the ______________ the temperature.
6. A change in temperature causes what?
7. What is the difference between boiling and evaporation?
8. What is sublimation?
9. Name the three ways thermal energy is transferred.
10. Sunburn is an example of what?
11. Give an example of convection.
12. What is conduction?
13. What is the difference between conductors and insulators?

Answers

2. The three phases of matter is solid, liquid, gas

Answer:

1.matter is any substance that has mass and takes up space by having volume.

2.The three fundamental phases of matter are solid, liquid, and gas (vapour),

3.In gases the particles move rapidly in all directions, frequently colliding with each other and the side of the container. With an increase in temperature, the particles gain kinetic energy and move faster. ... In liquids, particles are quite close together and move with random motion throughout the container.

3.In gases the particles move rapidly in all directions, frequently colliding with each other and the side of the container. With an increase in temperature, the particles gain kinetic energy and move faster. ... In liquids, particles are quite close together and move with random motion throughout the container.

The following problem applies to questions 8 and 9: a glass window acquires a net negative charge on its surface after being cleaned. Particles of dust, which are usually charged positively, start accelerating toward the window. If a particle travels a distance of 1 meter before reaching the window, in a time duration of 10 sec, and if the mass of the particle is 1 micro-gram and the charge on the particle is 10-12 Coulomb, then the magnitude of the electric field intensity is Group of answer choices

Answers

Answer:

the magnitude of the electric field intensity is 20 N/C

Explanation:

 Given the data in the question;

mass m = 1 micro gram = 1 × 10⁻⁹ kg

time duration t = 10 sec

distance s = 1 m

the charge on the particle q = 10⁻¹² Coulomb

force applied on a charged particle due to electric field E is;

F = Eq  ------ equ 1

where q is the charge on the particle.

Also, force on a particle with mass m  will be;

F = ma  ------ equ

where a is acceleration

so F = ma = Eq

ma = Eq -------- equ 3

using kinetic equation

Distance = 1/2×at²

where a is acceleration and t is the time period

now lets consider that initial velocity is zero (0)

Here;

1 m = 1/2 × a × ( 10 s )²

1 m = a × 50 s²

a = 1 m / 50 s²

a = 0.02 m/s²

so, from equation 3

ma = Eq

E = ma / q

we substitute

E = (1 × 10⁻⁹ kg × 0.02) / 10⁻¹² Coulomb

E = 2 × 10⁻¹¹ / 10⁻¹²

E = 20 N/C

Therefore, the magnitude of the electric field intensity is 20 N/C

A ray of light strikes a flat mirror at an angle of 40° from the perpendicular. The light is reflected at
what opposite angle to the same perpendicular line?
a) 40°
b) 50°
c) 30°
d) 60°

Answers

Answer:

a

Explanation:

angle of incidence equals angle of reflection on flat surface

Answer:

40 degress

Explanation:

What occurs as a ray of light passes from
al inilo water?

Answers

Answer:

this may be wrong but I am not sure

4. Name three examples of "concentrated" forms of energy.

Answers

Answer:

Nuclear power plant.

Gas stove.

Dam.

Gas pump.

Geothermal heat pump.

Power lines.

Solar panels.

Windmills.

Explanation:

Hope this helps :))

Answer:

gasoline,solar panels,geothermal heat pump,windmills

Explanation:

What happens when a moving object is moving a particular direction experiences a net force opposite the direction?

Answers

Answer:

stop

Explanation:

object stop

Answer:

If two forces of equal strength act on an object in opposite directions, the forces will cancel, resulting in a net force of zero and no movement. Two or more opposite forces are balanced forces if their effects cancel each other and they do not cause a change in an object's motion.

Consider a large truck carrying a heavy load, such as steel beams. A significant hazard for the driver is that the load may slide forward, crushing the cab, if the truck stops suddenly in an accident or even in braking. Assume, for example, that a 10 000-kg load sits on the flatbed of a 20 000-kg truck moving at 12.0 m/s. Assume that the load is not tied down to the truck, but has a coefficient of friction of 0.500 with the flatbed of the truck.
A) Calculate the minimum stopping distance for which the load will not slide forward relative to the truck.
B) Is any piece of data unnecessary for the solution?
a) mass of the load.
b) mass of the truck.
c) velocity.
d) coefficient of static friction.
e) all are necessary.

Answers

Answer:

A)

the minimum stopping distance for which the load will not slide forward relative to the truck is 14 m

B)

data that were not necessary to the solution are;

a) mass of truck and b) mass of load

Explanation:

Given that;

mass of load [tex]m_{LS}[/tex] = 10000 kg

mass of flat bed [tex]m_{FB}[/tex] = 20000 kg

initial speed of truck [tex]v_{0}[/tex] = 12 m/s

coefficient of friction between the load sits and flat bed μs = 0.5

A) the minimum stopping distance for which the load will not slide forward relative to the truck.

Now, using the expression

Fs,max = μs [tex]F_{N}[/tex]     -------------let this be equation 1

where [tex]F_{N}[/tex] = normal force = mg

so

Fs,max = μs mg

ma[tex]_{max}[/tex] = μs mg

divide through by mass

a[tex]_{max}[/tex] = μs g    ---------- let this be equation 2

in equation 2, we substitute in our values

a[tex]_{max}[/tex] = 0.5 × 9.8 m/s²

a[tex]_{max}[/tex] = 4.9 m/s²

now, from the third equation of motion

v² = u² + 2as

[tex]v_{f}[/tex]² = [tex]v_{0}[/tex]² + 2aΔx

where [tex]v_{f}[/tex] is final velocity ( 0 m/s )

a is acceleration( - 4.9 m/s² )

so we substitute

(0)² = (12 m/s)² + 2(- 4.9 m/s² )Δx

0 = 144 m²/s² - 9.8 m/s²Δx

9.8 m/s²Δx = 144 m²/s²

Δx = 144 m²/s² /  9.8 m/s²

Δx = 14 m

Therefore, the minimum stopping distance for which the load will not slide forward relative to the truck is 14 m

B) data that were not necessary to the solution are;

a) mass of truck and b) mass of load

An enormous thunderstorm covers Dallas-Ft. Worth. Your best friend Clark is a storm chaser and heads to the center of the storm to take some readings while you stay dry at home. While Clark is at the center of the storm, he sees and hears lightning strike a tree that is 190 m from where he is standing. You are 140 km from the tree. How long does it take for the sound to reach Clark

Answers

Answer:

407.61 seconds

Explanation:

Given that an enormous thunderstorm covers Dallas-Ft. Worth. Your best friend Clark is a storm chaser and heads to the center of the storm to take some readings while you stay dry at home. While Clark is at the center of the storm, he sees and hears lightning strike a tree that is 190 m from where he is standing. You are 140 km from the tree. How long does it take for the sound to reach Clark

Solution.

The distance between the Clark and you will be:

Distance = 140km - 190m

Distance = 140000 - 190

Distance = 139810 m

The radius of the earth is also considered but it will surely be insignificant as you subtracted the two distance values.

Using the formula

Speed = distance/time

Where

The speed of sound = 343 m/s

343 = 139810 / t

Make time the subject of formula

t = 139810 / 343

t = 407.61 s

Therefore, it will take 407.61 seconds for the sound to reach Clark

what is tangential velocity

Answers

Answer:

Tangential velocity is the linear speed of any object moving along a circular path

Explanation:

Answer:

Tangential velocity is the linear speed of any object moving along a circular path. A point on the outside edge of a turntable moves a greater distance in one complete rotation than a point near to the center.

Explanation:

i hope this helps and can i get brainliest pls?

An open pipe is 1.42 m long
What fundamental frequency
does it produce?
(Speed of sound = 343 m/s)
(Unit = Hz)

Answers

Answer:

the fundamental frequency produced by the open pipe is 120.78 Hz

Explanation:

Given;

length of the open pipe, L = 1.42 m

speed of sound in air, v = 343 m/s

The length of the open pipe for the fundamental frequency is equivalent to half of wavelength;

[tex]L = \frac{\lambda}{2} \\\\\lambda = 2L[/tex]

The fundamental frequency produced by the open pipe is calculated as;

[tex]f_o = \frac{v}{\lambda} \\\\f_o = \frac{v}{2L} \\\\f_o = \frac{343}{2 \times 1.42} \\\\f_o = 120.78 \ Hz[/tex]

Therefore, the fundamental frequency produced by the open pipe is 120.78 Hz

A 50 kg mass is sitting on a frictionless surface. An unknown constant force called force A pushes the mass for 2 seconds until the mass reaches a velocity of 3 m/s. If the 50 kg mass is now pushed by an unknown force B and reaches the velocity of 3 m/s in 4 seconds, compare the impulse delivered to the mass when acted upon by force A with the impulse delivered to the mass when acted on by force B? *

A) The impulse delivered to the mass when acted upon by force A is greater
B) The impulse delivered to the mass when acted upon by force B is greater
C) The impulse is the same in each case
D) We need to know the value of force A and force B in order to determine this

Answers

Answer:

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To determine the coefficient of static friction between two materials, an engineer places a small sample of one material on a horizontal disk whose surface is made of the other material and then rotates the disk from rest with a constant angular acceleration of 0.4 rad/s2. If she determines that the small sample slips on the disk after 9.903 s, what is the coefficient of friction

Answers

This question is incomplete, the missing image is uploaded along this answer.

Answer:

the coefficient of friction is 0.32

Explanation:

 Given the data in the question;

we make use of kinematic equation of motion;

ω = ω₀ + ∝t

we substitute

ω = ( 0 rad/s ) + ( 0.4 rad/s² )( 9.903 s )

ω = 3.9612 rad/s

The centripetal force acting on the sample is;

Fc = mrω²

from the image; r = 200 mm = 0.2 m

so we substitute

Fc = m(0.2 m ) ( 3.9612 rad/s )²

Fc = (3.13822 m/s²)m

we know that the frictional force between the two materials should be providing the necessary centripetal force to rotate the sample object;

f = Fc

μN = Fc

μmg = (3.13822 m/s²)m

μ = (3.13822 m/s²)m / mg

μ = (3.13822 m/s²) / g

acceleration due to gravity g = 9.8 m/s²

so

μ = (3.13822 m/s²) / 9.8 m/s²

μ = 0.32

Therefore, the coefficient of friction is 0.32

The half-life of radium-226 is 1590 years. (a) A sample of radium-226 has a mass of 100 mg. Find a formula for the mass of the sample that remains after t years. (b) Find the mass after 1000 years correct to the nearest milligram. (c) When will the mass be reduced to 40 mg? SOLUTION (a) Let m(t) be the mass of radium-226 (in milligrams) that remains after t years. Then dm/dt = km and m(0) = 100, so this theorem gives m(t) = m(0)ekt = ekt. In order to determine the value of k, we use the fact that m(1590) = 1 2 . Thus e1590k = so e1590k = and 1590k = ln 1 2 = − ln(2) k = . Therefore m(t) = . We could use the fact that eln(2) = 2 to write the expression for m(t) in the alternative form m(t) = . (b) The mass after 1000 years is as follows. (Round your final answer to the nearest milligram.) m(1000) = ≈ mg

Answers

Answer:

See explanation

Explanation:

a) Formula for the mass of the sample that remains after t years = N= Noe^-kt

Where;

N = mass at time t years

No = mass at time t= 0

k = decay constant

t = time taken

So,

N = 100e^-kt

b) First,

t1/2 = -ln(1/2)/k

t1/2 = 0.693/k

t1/2 = half life of radium-226 =1590 years

1590 = 0.693/k

k = 0.693/1590

k = 4.36 * 10^-4

So,

N= 100e^-(4.36 * 10^-4 * 1000)

N= 65 mg

c) From

N = 100e^-kt

40 = 100e^-(4.36 * 10^-4t)

40/100 = e^-(4.36 * 10^-4t)

0.4 = e^-(4.36 * 10^-4t)

ln(0.4) = ln(e^-(4.36 * 10^-4t))

-0.9163 = -4.36 * 10^-4t

t = 0.9163/4.36 * 10^-4

t = 2102 years

What is the magnitude of the electric field at the point (8.70 - 9.10 7.20 ) m if the electric potential is given by V

Answers

This question is incomplete, the complete question is;

What is the magnitude of the electric field at the point (8.70i - 9.10j + 7.20k ) m if the electric potential is given by V = 4.30xyz², where V is in volts and x, y  and z are in meters.

Answer:

the magnitude of the electric field is 5648.67 N/C

Explanation:

Given the data in the question;

Suppose electric field at this point is;

E = Exi + Eyj + Ezk

Now, electric field is given by;

E = -dV/dr

so,

Ex = -d( 4.30xyz² )/dx = -4.30yz²

Ey = -d( 4.30xyz² )/dy = -4.30xz²

Ez = -d( 4.30xyz² )/dz = -8.60xyz

so

E = -4.30yz² i  - 4.30xz² j - 8.60xyz k

now, at the point (8.70i - 9.10j + 7.20k )  

E = (-4.30(-9.10)(7.20)²) i  + (-4.30(8.70)(7.20)²) j + (-8.60(8.70)(-9.10)(7.20) k

E =  2028.499 i - 1939.334 j + 4902.206 k

so, Magnitude of electric field will be;

|E| = √( Ex² +  Ey² + Ez² )

we substitute

|E| = √( (2028.499)² +  (-1939.334)² + (4902.206)² )

|E| = √( 31907448.222993 )

|E| = 5648.67 N/C

Therefore, the magnitude of the electric field is 5648.67 N/C

Which one of the following statements concerning the buoyant force on an object submerged in a liquid is true?
A) The buoyant force depends on the mass of the object.
B) The buoyant force depends on the weight of the objeet.
C) The buoyant force is independent of the density of the liquid.
D) The buoyant force depends on the volume of the liquid displaced.
E) The buoyant force will increase with depth if the liquid is incompressible.

Answers

Answer:

D) The buoyant force depends on the volume of the liquid displaced.

Explanation:

Buoyancy can be defined as an upward force which is created by the water displaced by an object.

According to Archimede's principle, it is directly proportional to the amount (weight) of water that is being displaced by an object.

Thus, the greater the amount of water an object displaces; the greater is the force of buoyancy pushing the object up.

The buoyancy of an object is given by the formula;

[tex] Fb = pgV [/tex]

[tex] But, \; V = Ah [/tex]

[tex] Hence, \; Fb = pgAh [/tex]

Where;

Fb = buoyant force of a liquid acting on an object.g = acceleration due to gravity. p = density of the liquid.v = volume of the liquid displaced. h = height of liquid (water) displaced by an object. A = surface area of the floating object.

The unit of measurement for buoyancy is Newton (N).

Additionally, the density of a fluid is directly proportional to the buoyant force acting on it i.e as the density of a liquid decreases, buoyancy decreases and vice-versa.

Hence, the statement concerning the buoyant force on an object submerged in a liquid which is true is that the buoyant force depends on the volume of the liquid displaced.

If an object is completely submerged, the volume of the object is equal to the volume of liquid displaced.

A 7.80 g bullet has a speed of 620 m/s when it hits a target, causing the target to move 6.30 cm in the direction of the bullet's velocity before stopping. (a) Use work and energy considerations to find the average force (in N) that stops the bullet. (Enter the magnitude.) N (b) Assuming the force is constant, determine how much time elapses (in s) between the moment the bullet strikes the target and the moment it stops moving. s

Answers

Answer:

[tex]23796.19\ \text{N}[/tex]

[tex]0.0002032\ \text{s}[/tex]

Explanation:

F = Force

s = Displacement = 6.3 cm

m = Mass of bullet = 7.8 g

v = Velocity of bullet = 620 m/s

t = Time taken

Work done is given by

[tex]W=Fs[/tex]

Kinetic energy is given by

[tex]K=\dfrac{1}{2}mv^2[/tex]

Using work energy considerations we get

[tex]Fs=\dfrac{1}{2}mv^2\\\Rightarrow F=\dfrac{1}{2s}mv^2\\\Rightarrow F=\dfrac{1}{2\times 0.063}\times 7.8\times 10^{-3}\times 620^2\\\Rightarrow F=23796.19\ \text{N}[/tex]

The average force that stops the bullet is [tex]23796.19\ \text{N}[/tex].

Force is given by

[tex]F=m\dfrac{v-u}{t}\\\Rightarrow t=m\dfrac{v-u}{F}\\\Rightarrow t=7.8\times 10^{-3}\times \dfrac{620}{23796.19}\\\Rightarrow t=0.0002032\ \text{s}[/tex]

The time taken to stop the bullet is [tex]0.0002032\ \text{s}[/tex].

Question 1 of 10
Which object has the most gravitational potential energy?

A. A 8 kg book at a height of 2 m
B. An 8 kg book at a height of 3 m
C. An 5 kg book at a height of 3 m
D. A5 kg book at a height of 2 m
SUBMIT

Answers

Answer:

B = An 8 kg book at a height of 3 m

I think the answer is B

[O.05]Which of these Earth spheres interact with oceans during beach erosion?

geosphere
hydrosphere
cryosphere
atmosphere

Answers

Answer:

hydrosphere of these Earth spheres interact with oceans during beach erosion.

Answer:

Geosphere

Explanation:

The geosphere is the solid parts of the earth including rocks, minerals, and sand on the beach. The shoreline is where the geosphere meets the ocean. This is how they interact during erosion.

It is not the hydrosphere because the ocean is a part of the hydrosphere.

A 10 kg object moving to the left collides with and sticks to a 3 kg object moving to the right. Which of the following is true of the motion of the combined objects immediately after the collision?

Answers

Answer:

"Cannot be determined," if that's an answer choice. It depends on the velocities of both objects, since momentum=mass*velocity.

Explanation:

what is the mass of a ball rolling at 4.5m/s if it's momentum is 3.5 kg•m/s?​

Answers

Answer:

The ball has a mass of 7/9 kg

Explanation:

Momentum is just mass times velocity, so to find its mass, we can simply divide the given momentum by the given velocity.

[tex]3.5 kg\frac{m}{s} \div 4.5\frac{m}{s} = \frac{7}{9}kg[/tex]

cosmic Microwave Background radiation is one piece of supporting evidence for the Big Band Theory. Are these microwaves at the longer or shorter end of the spectrum?


are they long or short?

Answers

Answer:

it is long.

Explanation:

I know the answer but I don't know how to explain it

As a sports car travels along a level stretch of road with constant speed, most of the power developed by the engine is used to compensate for the energy transformations due to friction forces exerted on the sports car by the air and the road. If the power developed by the engine is 0.824 hp, calculate the total friction force acting on the sports car (in N) when it is moving at a speed of 30 m/s. One horsepower equals 746 W.

Answers

Answer:

20.49 N

Explanation:

From the question given above, the following data were obtained:

Power (P) = 0.824 hp

Velocity (v) = 30 m/s

1 h = 746 W

Force (F) =?

Next, we shall convert 0.824 hp to Watts (W). This can be obtained as follow:

1 h = 746 W

Therefore,

0.824 hp = 0.824 hp × 746 W / 1 h

0.824 hp = 614.704 W

Finally, we shall determine the force as follow:

Power (P) = 614.704 W

Velocity (v) = 30 m/s

Force (F) =?

P = F × v

614.704 = F × 30

Divide both side by 30

F = 614.704 / 30

F = 20.49 N

A 1000 kg truck moving at 2.0 m/s runs into a concrete wall. It takes 0.5 s for the truck to completely stop. What is the magnitude of force exerted on the truck during the collision?​

Answers

Answer:

Momentum is given by

p

=

m

v

. Impulse is the change of momentum,

I

=

Δ

p

and is also equal to force times time:

I

=

F

t

. Rearranging,

F

=

I

t

=

Δ

p

t

=

0

20

,

000

5

=

4000

N

.

Explanation:

Momentum before the collision is

p

=

m

v

=

2000

10

=

20

,

000

k

g

m

s

1

.

Assuming the truck comes to a complete halt, the momentum after the collision is

0

k

g

m

s

1

.

The change in momentum,

Δ

p

, is initial minus final

0

20

,

000

=

20

,

000

This is called the impulse:

I

=

Δ

p

. Impulse is also equal (check the units) to force times time:

I

=

F

t

.

We can rearrange this expression to make

F

the subject:

F

=

I

t

=

Δ

p

t

=

20

,

000

5

=

4000

N

The negative sign just means the force acting is in the opposite direction to the initial momentum.

(This will be the average force acting during the collision: collisions are chaotic so the force is unlikely to be constant.)

a rugby player passes the ball 5.34 m across the field, where it is caught at the same height as it left his hand. at what angle was the ball thrown if its initial speed was 7.7 m/s, assuming that the smaller of the two possible angles was used

Answers

Answer:

[tex]31.035^{\circ}[/tex]

Explanation:

x = Displacement in x direction = 5.34 m

t = Time taken to travel the displacement

y = Displacement in y direction = 0

u = Initial velocity of ball = 7.7 m/s

g = Acceleration due to gravity = [tex]9.81\ \text{m/s}^2[/tex]

Displacement in x direction is given by

[tex]x=u\cos\theta t\\\Rightarrow t=\dfrac{5.34}{7.7 \cos\theta}[/tex]

Displacement in y direction is given by

[tex]y=u\sin\theta t-\dfrac{1}{2}gt^2\\\Rightarrow 0=7.7\sin\theta \dfrac{5.34}{7.7\cos\theta}-\dfrac{1}{2}\times 9.81 (\dfrac{5.34}{7.7\cos\theta})^2\\\Rightarrow 0=7.7\sin\theta-4.905\times \dfrac{5.34}{7.7\cos\theta}\\\Rightarrow 0=7.7^2\sin\theta \cos\theta-4.905\times 5.34\\\Rightarrow 0=7.7^2\dfrac{\sin2\theta}{2}-4.905\times 5.34\\\Rightarrow 0=7.7^2\sin2\theta-4.905\times5.34\times 2\\\Rightarrow \sin2\theta=\dfrac{4.905\times 5.34\times 2}{7.7^2}\\\Rightarrow 2\theta=\sin^{-1}\dfrac{4.905\times 5.34\times 2}{7.7^2}[/tex]

[tex]\Rightarrow \theta=\dfrac{62.07}{2}\\\Rightarrow \theta=31.035^{\circ}[/tex]

The angle at which the ball was thrown is [tex]31.035^{\circ}[/tex].

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