Physics IA Worksheet #2 on Accelerated Motion and Forces

1. A car accelerates from rest to a speed of 40 m/s in 15 seconds. If the net force which creates the acceleration is 2,000 N, what is the car’s mass ?

2. A driver in a Porsche 944 is tooling down a country road at a speed of 20 m/s, when a moose lurches out into the road, a distance of 60 meters ahead of him. If the mass of his car is 1545 kg, and its brakes are capable of applying 7,725 N of force without skidding, does he stop in time to avoid the moose, or not ?

3. Sergei tees off on a stationary hockey puck using his most powerful slap shot. If he can exert a force of 250 N on the 500 gram puck for a time of 0.1 seconds, what velocity will he give to it, and how far will the puck move in the time it is on his stick ?

4. A gun with a 1.2 meter barrel shoots a 50 gram bullet so that it accelerates from rest to a velocity of 850 m/s. What force must the bullet have experienced as it was shot ? Assume that the bullet speeds uniformly as it travels the length of the gun barrel.

5. Chris is capable of exerting a constant force of 500 N on the pedals of his bike which, along with his body, has a mass of 75 kg. Starting from rest, how fast will Chris be going after a two seconds’ time ? How far will he have gone in his time ?

6. A 1,000 kg car was parked on a hill the other day when its parking brake let go. It rolled down the hill, accelerating to a speed of 10 m/s before it zipped through an intersection and smashed into a guard rail. If the guard rail was pushed back a distance of 1.5 meters as a result of the collision, what acceleration did the car experience, and how much force must the guard rail have supplied to it as it slowed down ?

7. Shaquille O’Neal leaps for a rebound and lands at a rate of 2 m/s. As he lands, he does not bend his knees, but instead lets the compression of his shoes provide the cushion to slow his momentum. What force will act on his legs as his 120 kg body is stopped in a distance of only 0.5 cm ? How many times larger than his own body weight is this force ?

8. Based on your answer to the above question, you should conclude that it would be very dangerous for any person to try to land with their knees locked. Even still, landing after a jump can demand a lot of force from your legs even if you do it correctly. If you were to have Shaq try the same jump as above, and only use a force equal to twice his body weight to stop himself, how much would his knees have to bend ? Is this realistically possible ?

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