Physics Test 3 answers

A 1.0 kg ball drops vertically onto a floor, hitting with a speed of vi = 24 m/s. It rebounds with a speed of vf = -24 m/s. The ball is in contact with the floor for 0.12 s. The magnitude of the average force on the ball was

- 400 N

A 1.0 kg ball drops vertically onto a floor, hitting with a speed of vi = 24 m/s. It rebounds with a speed of vf = -24 m/s. The ball is in contact with the floor for 0.12 s. The magnitude of the maximum force on the ball was approximately

- 800 N

A 1.0 kg ball drops vertically onto a floor, hitting with a speed of vi = 24 m/s. It rebounds with a speed of vf = -24 m/s. The ball is in contact with the floor for 0.12 s. The change in momentum of the ball (in kgm/s) was

-48

A 1.0 kg ball drops vertically onto a floor, hitting with a speed of vi = 24 m/s. It rebounds with a speed of vf = -24 m/s. The ball is in contact with the floor for 0.12 s. The impulse to the ball (in Ns) was

-48

Three children are balanced on a seesaw as shown. The fulcrum is located below the center of mass of the seesaw. The length of the seesaw is 6.0 m. The torque (in N m) supplied by the seesaw is equal to

0

A 400 g mass, m1, is balanced at the end of a 100g meter stick as shown. If r1 is increased, the system rotates counterclockwise. Assume the center of mass of the meter stick is at the 50 cm mark and m1 is at the 0 cm mark. The value of the counterclockwise torque (in Nm) is

0.39

In exercise physiology studies, it is sometimes important to determine the location of a person's center of mass. This determination can be done with the arrangement shown. A light plank rests on two scales, which read Fg1 = 400 N and Fg2 = 300 N. A distance of 1.65 m separates the scales . How far from the woman's feet is her center of mass?

0.943 m

Three children are balanced on a seesaw as shown. The fulcrum is located below the center of mass of the seesaw. The length of the seesaw is 6.0 m. The value of x is

1.5 m

A 400 g mass, m1, is balanced at the end of a 100g meter stick as shown. If r1 is increased, the system rotates counterclockwise. Assume the center of mass of the meter stick is at the 50 cm mark and m1 is at the 0 cm mark. The value of r1 (in cm) is

10

The ballistics pendulum shown is used to determine the velocity of a bullet. The mass of the bullet = 50.0 grams. the mass of the pendulum = 500 grams. The height, h = 4.50 cm. The value of v (in m/s) is equal to

10.3

A cart of mass 2.0 kg, moving at a constant velocity of 6.0 m/s collides head on with a stationary 1.0 kg cart. The two carts stick together and move off in a straight line at velocity v'. The total momentum (in kg m/s) of the system before the collision was

12.0

A cart of mass 2.0 kg, moving at a constant velocity of 6.0 m/s collides head on with a stationary 1.0 kg cart. The two carts stick together and move off in a straight line at velocity v'. The total momentum of the system after the collision was

12.0

The moment of inertia, I, of the merry-go-round in kg m2 equals

146

Three children are balanced on a seesaw as shown. The fulcrum is located below the center of mass of the seesaw. The length of the seesaw is 6.0 m. The total clockwise torque (in N m) is

1800

The force, F, acting on the merry-go-round in N equals

195

The angular acceleration of the merry-go-round in rad/s2 equals

2

A hockey puck B rests on a smooth ice surface and is struck by a second puck A moving at 30.0 m/s. Both move off at angles of 45o with the original direction of A. The pucks have equal masses of .200 kg each. The speed of puck A (in m/s) after the collision was

21.2

The torque acting on the merry-go-round in Nm equals

292

If the merry-go-round were in the shape of ring instead of a disk the, F, would be

2F

A cart of mass 2.0 kg, moving at a constant velocity of 6.0 m/s collides head on with a stationary 1.0 kg cart. The two carts stick together and move off in a straight line at velocity v'. The velocity, v', (in m/s) of the masses after the collision was

4.0

A hockey puck B rests on a smooth ice surface and is struck by a second puck A moving at 30.0 m/s. Both move off at angles of 45o with the original direction of A. The pucks have equal masses of .200 kg each. The magnitude of the total momentum (kg m/s) before the collision was

6

A hockey puck B rests on a smooth ice surface and is struck by a second puck A moving at 30.0 m/s. Both move off at angles of 45o with the original direction of A. The pucks have equalmasses of .200 kg each. The magnitude of the total momentum (kg m/s) after the collision was

6

In exercise physiology studies, it is sometimes important to determine the location of a person's center of mass. This determination can be done with the arrangement shown. A light plank rests on two scales, which read Fg1 = 400 N and Fg2 = 300 N. A distance of 1.65 m separates the scales . How much does the woman weigh?

700 N

The two rigid objects shown in the figure have the same mass and radius. If they are initially at rest and same torque is applied to each for the same amount of time, which will be rotating faster?

A

The two rigid objects shown in the figure have the same mass and radius. Which of the two has the greater Moment of Inertia?

B

An object moves in a circular path with constant speed v. Which of the following statements is true?

Both its velocity and acceleration are changing.

A student is rotating at a constant angular velocity while holding two weights as shown. If the weights are moved outward, the angular velocity will decrease. The reason for this is that

Both the angular momentum is conserved and the moment of inertia of the student increases.

The ballistics pendulum shown is used to determine the velocity of a bullet. Which of the following is not true.

KEA = KEB

Three equal masses collide as shown Which of the following statements is true

The magnitude of v3 is greater than the magnitude of v2

Angular acceleration and centripetal acceleration are the same.

false

For the previous answer to be correct, all three must have the same mass.

false

Increasing the impact time in a collision increases the impact force

false

The moment of inertia of a disk is greater than the moment of inertia of a ring

false

The moment of inertia of an object is a vector.

false

Three equal masses collide as shown This was an elastic collision.

false

Andrea and Chuck are riding on a merry-go-round. Andrea rides on a horse at the outer rim of the circular platform, twice as far from the center of the circular platform as Chuck, who rides on an inner horse. Chuck's translational speed is

half of Andrea's

If global warming continues, it's likely that some ice from the polar ice caps of the Earth will melt and the water will be distributed closer to the Equator. If this occurs, would the length of the day (one revolution)

increase

A cart of mass 2.0 kg, moving at a constant velocity of 6.0 m/s collides head on with a stationary 1.0 kg cart. The two carts stick together and move off in a straight line at velocity v'. The total kinetic energy of the system after the collision was ___ before the collision .

less than

The stability of an object can be increased by __ the center of mass.

lowering

A solid ball, a disk, and a ring all roll down an incline as shown. Assume that all start from rest from the same starting point on the incline. The one that reaches the bottom first is

the ball

Andrea and Chuck are riding on a merry-go-round. Andrea rides on a horse at the outer rim of the circular platform, twice as far from the center of the circular platform as Chuck, who rides on an inner horse. When the merry-go-round is rotating at a constant angular speed, Chuck's's angular speed is

the same as Andrea's

A hockey puck B rests on a smooth ice surface and is struck by a second puck A moving at 30.0 m/s. Both move off at angles of 45o with the original direction of A. The pucks have equalmasses of .200 kg each. The direction of the total momentum of the system after the collision was

to the right

A 400 g mass, m1, is balanced at the end of a 100,g meter stick as shown. If r1 is increased, the system rotates counterclockwise. Assume the center of mass of the meter stick is at the 50 cm mark and m1 is at the 0 cm mark. The clockwise torque is supplied by the meter stick.

true

An object is in rotational equilibrium when the net torque on the object is zero.

true

Angular velocity is a vector.

true

In an elastic collision the maximum impact force is approximately equal to twice the average impact force.

true

Kinetic energy is conserved in elastic but not in inelastic collisions

true

Momentum is a vector but kinetic energy is a scalar

true

Momentum is conserved in both elastic and inelastic collisions.

true

The center of mass of an object can be inside or outside the object.

true