T4 Wk 4 - Circular Motion

A ball is being whirled in a horizontal circle of radius r at constant speed. The velocity of the ball at positions A and B is shown in Figure 1. Select the direction that best describes the change in velocity of the ball from point A to point B.

• A ↖

• B ↘

• C ↗

• D ↙

Select the diagram in Figure 2 that best shows the relationship between centripetal force (vertical axis) and the velocity of an object being whirled in a horizontal circle at constant speed.

• A

• B

• C

• D

A student is investigating centripetal motion by whirling a rubber stopper above his head in a horizontal circle at constant speed (Figure 3). If the student increases the hanging slotted masses (M), select the statement that best describes what he can do to keep the radius constant.

• increase m or v
• increase m or decrease v

• decrease m or increase v

• decrease m or v

A rubber stopper is moving in an anticlockwise horizontal circle at constant speed. Select the diagram in Figure 4 that shows the direction of the velocity and acceleration at point X.

• A

• B

• C

• D

What is the difference between uniform and non-uniform circular motion?

• Uniform circular motion has constant speed, while non-uniform circular motion has varying speed.

• Uniform circular motion has varying speed, while non-uniform circular motion has constant speed.

• Both have constant speed but different directions.

• Both have varying speed and direction.

Determine whether this is true: An object will travel the circumference of a circle in one period (T) of time if it is in uniform circular motion.

• True

• False

A ball on a string is swirled around in a horizontal circle at a constant speed of 2.5 m s⁻¹ and experiences an acceleration of 3.9 m s⁻². Calculate the radius of its motion.

• 1.60 m

• 1.28 m

• 0.32 m

• 0.96 m

A rock is swung in a horizontal circle on a 1.2 m length of string. It has a constant speed of 3.3 m s⁻¹. What is the centripetal acceleration of the rock?

• 9.075 m s⁻²

• 8.25 m s⁻²

• 7.5 m s⁻²

• 6.25 m s⁻²

Describe the type of force necessary to keep the Moon in orbit around Earth.

• Gravitational force

• Electromagnetic force

• Nuclear force

• Frictional force

Describe the type of force necessary to keep a car from sliding sideways off a circular track.

• Frictional force

• Gravitational force

• Centripetal force

• Magnetic force