PhysicsTest #5Name:

  1. A tennis ball leaves the top of a racketnwith a speed ,of 60 m/sec. If the ball’s maass is 60 ,g and it is in conact with the racket for .03 secs what is the average force on the ball?
  1. A child throws a 4.0 kg package from a boat with a horizontal speed of 9.0 m/sec. Calculate the speed of the boat assuming that it was initially at rest. The mass of the child is 22 kg and that of the boat is 55.0 kg.
  1. A 140kg tackler collides headon with and tackles a 90 kg halfback running at 6.5.m/sec.

a)What is their mutual speed immediately after the collision?

b)Is the collision elastic, inelastic or totally inelastic? Support your answer with words AND calculation.

  1. A 4 kg object moving at 5 m/sec collides with a 10 kg object initially at rest. What is the speed of both objects after they collide. Assume an elastic collision.
  1. A gun is fired vertically into a 2.4 kg block of wood at rest directly above it. If the bullet has a mass of 20g and a speed of 350 m/sec how high will the block rise in the air?

6. A merry-go-round is a uniform disk of radius 10 m and mass 40,000 kg.Find its:

a) moment of inertia

b) the torque needed to accelerate it from rest to 20 rpm in 4.00 sec.

7. A 5.0 m diameter merry go round is rotating with an angular velocity of 1.00 rad/sec. Its total moment of inertia is 2000 kgm2.Then 3 people of mass 50 kg suddenly step on the edge of the merry-go-round. What is the angular velocity of the merry-go-round now?

8. A ball rolls down a ramp. If the vertical drop is 3.5 m what is its speed at the bottom of the ramp?

9. A phonograph turntable reaches its rated speed of 33 rpm after 2.5 revolutions. What is its angular acceleration?

Part II.

1. Write down 2 kinematics equations and their rotational counterparts.

2. What are the units for rotational kinetic energy?

3. Explain why a spinning top falls over.

4. Which has more inertia: ring or a disk. Both have the same mass and radius. Explain in words why.

5.When a spinning ballerina extends her arms which of the following increase: L,I,w,?

B1. Here is some data from the Gravitational=Rotational Energy Lab that involved the platter. I=.00747 kgm2.rplatter=.127m. rspindle=2.00cm. Falling mass and hanger: 105g. a)If the velocity measured by the computer was 1.7 m/sec find the rotational kinetic energy of the platter. b) Find the kinetic energy of the falling mass.

B2. A bullet of mass .0020 kg travelling at 300m/sec strikes the center of a 3.0kg block of wood which is sitting on a fence post. The block of wood is 2.0 m above the ground. The bullet remains embedded in the block.

a)Determine the velocity of the bullet + block

b) how far from the base of the fence the bullet+ block lands.

B3. Physics of Dance).By first lifting and then dropping his legs the young Micharl Jordan appeared to defy gravity. Explain how the

Illusion works.