Chapter 7 Quick Check

Problems

Quick Check 7.1

A ball rolls around a circular track with an angular velocity of 4 rad/s. What is the period of the motion?

A. sB. 1 sC. 2 sD. sE. s

Quick Check 7.2

Rasheed and Sofia are riding a merry-go-round that is spinning steadily. Sofia is twice as far from the axis as is Rasheed. Sofia’s angular speed is ______ that of Rasheed.

A. HalfB. The same asC. TwiceD. Four timesE. We can’t say without

knowing their radii.

Quick Check 7.3

Rasheed and Sofia are riding a merry-go-round that is spinning steadily. Sofia is twice as far from the axis as is Rasheed. Sofia’s speed is ______ that of Rasheed.

A. HalfB. The same asC. TwiceD. Four timesE. We can’t say without

knowing their radii.

Quick Check 7.5

The fan blade is slowing down. What are the signs of ω and ?

A. ω is positive and is positive.B. ω is positive and is negative.C. ω is negative and is positive.D. ω is negative and is negative.E. ω is positive and is zero.

Quick Check 7.6

The fan blade is speeding up. What are the signs of and ?

A. is positive and is positive.B. is positive and is negative. C. is negative and is positive. D. is negative and is negative.

Quick Check 7.8

Starting from rest, a wheel with constant angular acceleration spins up to 25 rpm in a time t. What will its angular velocity be after time 2t?

A. 25 rpmB. 50 rpmC. 75 rpmD.100 rpmE. 200 rpm

Quick Check 7.10

The four forces shown have the same strength. Which force would be most effective in opening the door?

A. Force F1

B. Force F2

C. Force F3

D. Force F4

E. Either F1 or F3

Stop to Think 7.3

A wheel turns freely on an axel on the center. Which of the given forces will provide the largest positive torque on the wheel?

A. AB. BC. CD. DE. E

Chapter 9 Quick Check

Problems

Stop to Think 9.1

Which force delivers a greater impulse?

A. Force AB. Force BC. Both deliver

the same impulse

Quick Check 9.2

A 2.0 kg object moving to the right with speed 0.50 m/s experiences the force shown. What are the object’s speed and direction after the force ends?

A. 0.50 m/s leftB. At restC. 0.50 m/s rightD.1.0 m/s rightE. 2.0 m/s right

Quick Check 9.3

A 2.0 kg object moving to the right with speed 0.50 m/s experiences the force shown. What are the object’s speed and direction after the force ends?

A. 0.50 m/s leftB. At restC. 0.50 m/s rightD.1.0 m/s rightE. 2.0 m/s right

Quick Check 9.5

A light plastic cart and a heavy steel cart are both pushed with the same force for 1.0 s, starting from rest. After the force is removed, the momentum of the light plastic cart is ________ that of the heavy steel cart.

A. Greater thanB. Equal toC. Less thanD. Can’t say. It depends on the size of the force.

Quick Check 9.1

The cart’s change of momentum px is

A. –20 kg m/sB. –10 kg m/sC. 0 kg m/sD.10 kg m/sE. 30 kg m/s

Quick Check 9.7

You awake in the night to find that your living room is on fire. Your one chance to save yourself is to throw something that will hit the back of your bedroom door and close it, giving you a few seconds to escape out the window. You happen to have both a sticky ball of clay and a super-bouncy Superball next to your bed, both the same size and same mass. You’ve only time to throw one. Which will it be? Your life depends on making the right choice!

A. Throw the Superball.B. Throw the ball of clay.C. It doesn’t matter. Throw either.

Quick Check 9.8

A mosquito and a truck have a head-on collision. Splat! Which has a larger change of momentum?

A. The mosquitoB. The truckC. They have the same change of momentum.D.Can’t say without knowing their initial velocities.

Quick Check 9.10

The two boxes are on a frictionless surface. They had been sitting together at rest, but an explosion between them has just pushed them apart. How fast is the 2-kg box going?

A. 1 m/s B. 2 m/sC. 4 m/sD. 8 m/sE. Not enough information.

Quick Check 9.11

The 1-kg box is sliding along a frictionless surface. It collides with and sticks to the 2-kg box. Afterward, the speed of the two boxes is

A. 0 m/s B. 1 m/sC. 2 m/sD.3 m/sE. There’s not enough information to tell.

Chapter 10 Quick Check Problems(coming soon)