2.5.1 Describing Uniform Circular Motion

Question 1

Describing Uniform Circular Motion

Answer 1

• For uniform circular motion, position can be described by an angle q and a distance R from the origin. In Cartesian coordinates: and .
• In uniform circular motion, the direction of the velocity vector is tangent to the circle.
• For an object in uniform circular motion, the magnitude of its acceleration vector is . The direction of the acceleration vector is centripetal or towards the center.

Question 2

Which of the following is not a good example of uniform circular motion?

Answer 2

a person taking off on an airplane to fly around the world on a path defined by the equator

Question 3

In uniform circular motion, acceleration is defined as a = dv/dt. This equation implies that the velocity vector changes constantly. Why is this true?

Answer 3

The direction of the velocity vector changes constantly.

Question 4

Which of the following is not correct?

Answer 4

f = 2T = frequency: the number of revolutions around a circle per second.

Question 5

Which way does the acceleration point in uniform circular motion? What would happen if the acceleration suddenly equaled 0 m / s2?

Answer 5

The acceleration vector points toward the center of the circle. If the acceleration suddenly disappeared, the object would move in the direction indicated by v

Question 6

Which of the following statements about the uniform circular motion of an object is not correct?

Answer 6

At any instant in time, x = rsinu and y = rcosu

Question 7

In uniform circular motion, the average velocity is a = v^2/r. Which of the following statements about the derivation of this relationship is not correct.

Answer 7

as delta t -> 0, (delta r/ delta t) -> a, the instantaneous acceleration

Question 8

Which of the following statements related to uniform circular motion is not correct?

Answer 8

If an object in uniform circular motion moves quickly and the radius of the circle is small, its acceleration will also be small.

Question 9

Which of the following does not give the correct speed, v, for a merry-go-round with the given T and r values?

Answer 9

T = 8.0 s
r = 3.0 m
v = 19 m / s