Exam 8: Linear Momentum and Collisions

A child bounces a 50-gram superball on the sidewalk. The velocity of the superball changes from 21 m/s downward to 19 m/s upward. If the contact time with the sidewalk is 1/800 s, what is the magnitude of the force exerted on the superball by the sidewalk?

A 6.0-kg object moving 5.0 m/s collides with and sticks to a 2.0-kg object. After the collision the composite object is moving 2.0 m/s in a direction opposite to the initial direction of motion of the 6.0-kg object. Determine the speed of the 2.0-kg object before the collision.

Refer to Exhibit 8-1 below.Exhibit 8-1 Two birds of prey hurtling after the same rabbit collide in mid-air and grab each other with their talons. Each 250-g bird is flying at 30 m/s at a 60 $\degree$ angle to the ground. What is the magnitude of their total momentum, in $\frac{\mathrm{kg} \cdot \mathrm{~m}}{\mathrm{~s}}$ , immediately after the collision?

Assume that the average mass of each of the approximately 1 billion people in China is 55 kg. Assume that they all gather in one place and climb to the top of 2-m high ladders. The centre of mass of the Earth (mE = 5.90 $\times$ 1024 kg) is then displaced:

Three particles are placed in the xy plane. A 30-g particle is located at (3, 4) m, and a 40-g particle is located at (-2, -2) m. Where must a 20-g particle be placed so that the centre of mass of the three-particle system is at the origin?

A 5.0-g particle moving 60 m/s collides with a 2.0-g particle initially at rest. After the collision each of the particles has a velocity that is directed 30 $\degree$ from the original direction of motion of the 5.0-g particle. What is the speed of the 2.0-g particle after the collision?

A 3.0-kg ball with an initial velocity of (4 + 3 ) m/s collides with a wall and rebounds with a velocity of (-4 + 3 ) m/s. What is the impulse exerted on the ball by the wall?