Conceptual Physics Midterm 2016 (1-9)

Describe some part of the event that applies Newton's 2nd Law not yet covered.

since the car has much more mass then you do that means that the car will accelerate less then you will

When a car is sitting still, what forces act on the car? What is the net force acting on the car?

support force, and gravity which would make it 0

*Use Newton's Laws to explain your answer* ( hint acceleration= change of velocity/time) Your car goes from 0 m/s to 20 m/s in 5 seconds. What is the acceleration?

(20-0)/5----> 4s=A

3000 kg car A is sitting at a red light. 9000 kg car B going 24m/s runs into it. What is the speed of the tangled cars after the collision?

(3,000kg)(0m/s) + (9,000kg)(24m/s)=(3,000kg) + (9,000kg)V-------> 18m/s=V

*Use Newton's Laws to explain your answer* ( hint acceleration= change of velocity/time) Your car goes from 20 m/s to 32 m/s in 4 seconds What is the acceleration?

(32-20)/4-----> 3 s=A

3000 kg car A is sitting at a red light. 9000 kg car B going 24m/s runs into it. (hint: Newton's 2nd Law) Calculate the amount of force was applied to car B during the collision.

-20(9,000)=-180,00 Newtons

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Now you are riding on the interstate at 70mph. you toss a ball up in the air. At the top of its path, what is the speed of the ball?

0 m/s

You are sitting in a car a car that is not moving. You toss a ball up in the air and catch it. At the top of its path, what is the speed of the ball?

0 m/s

Now you are riding on the interstate at 70mph. you toss a ball up in the air. At the top of its path, what is the acceleration?

10 m/s^2

You are sitting in a car a car that is not moving. You toss a ball up in the air and catch it. At the top of its path, what is the acceleration of the ball?

10 m/s^2

3000 kg car A is sitting at a red light. 9000 kg car B going 24m/s runs into it. (hint: Newton's 2nd Law) Calculate the amount of force was applied to car A during the collision.-20

18(3,000)= 180,00 Newtons

3000 kg car A is sitting at a red light. 9000 kg car B going 24m/s runs into it. ( hint acceleration= change of velocity/time) If the collision lasts 0.3 s, what is car A's acceleration during the collision?

A=(18-0)/.3----> 60m/s^2

3000 kg car A is sitting at a red light. 9000 kg car B going 24m/s runs into it. (hint acceleration =change of velocity/ time) If the collision lasts 0.3 s, what is car B's during the collision?

B=(24-18)/.3---> -20m/s^2

Now you are riding on the interstate at 70mph. you toss a ball up in the air. What forces are acting on the ball?

Gravity

You are sitting in a car a car that is not moving. You toss a ball up in the air and catch it. What forces are acting on it?

Gravity

Modern cars have air bags and crumple zones. How do these protect the people in the car during collisions?

It means that the vehicle would have more impulse which means that it would have more time so that the force will not be as great

If the cars had been more rigid the time of the collision would have been reduced. What effect would that have had on you?

It would mean you would have more force and less time which means that the people in the vehicle will most likely get more injuries

Now you are riding on the interstate at 70mph. you toss a ball up in the air. can you catch it or will it land behind you? Explain.

No, because the ball is moving that same speed as you

You are sitting in a car a car that is not moving. You toss a ball up in the air and catch it. Is the ball accelerating?( justify your answer)

Yes, because the velocity is changing.

Describe some part of the event that applies Newton's 1st Law not yet covered.

You could go through the window, because an object at rest stays rest unless there is an unbalance force, which means which that your body wants to stay at rest but since car was hit by an unexpected force which forced your body to go into motion

A car is moving at a constant speed of 70 mph on a straight flat road. What forces act on the car? What net force acts on the car?

air resistance, gravity , support force, friction

A car slams on the brakes and skids to a stop. What force act on the car? What net force acts on the car?

friction, air resistance, support force and gravity

3000 kg car A is sitting at a red light. 9000 kg car B going 24m/s runs into it. Which car experiences more force? Explain. (hint: Newton's 3rd Law)

it is the same, because if Car A puts a force on Car B then Car B puts a Force Car A.

"motion is relative". What does that mean? Use examples.

it means that everything is compared to something stationary

What is different and what is the same about the ball's motion when the car is moving?

it would be determined by the frame of reference, because if it was you throwing the ball it would look different but if you were outside of the car if would look much different

What if the ball goes out the window? Describe its motion.

the ball would go 70mph still but will stop soon because of multiple factors, like that gravity will bring it closer to the ground will act a force onto to it and also of air resistance and friction to make it stop moving

Now you are riding on the interstate at 70mph. you toss a ball up in the air. Is the ball accelerating? Justify your answer.

yes because the balls is changing

3000 kg car A is sitting at a red light. 9000 kg car B going 24m/s runs into it. Did car B accelerate? why or why not?

yes because the cars velocity changed

3000 kg car A is sitting at a red light. 9000 kg car B going 24m/s runs into it. Did the momentum of car A change? why or why not?

yes because there velocity changed

3000 kg car A is sitting at a red light. 9000 kg car B going 24m/s runs into it. Did the momentum of car B change? Why or not?

yes because there velocity changed

3000 kg car A is sitting at a red light. 9000 kg car B going 24m/s runs into it. Did car A accelerate? why or why not?

yes, because the cars velocity changed