3.4.2 Solving Circular Motion Problems

Question 1

Solving Circular Motion Problems

Answer 1

• When solving problems, any criterion for which the normal force is negative violates the equations of uniform circular motion.
• The minimum speed with which a bucket full of water must rotate so that the water remains in the bucket is .
• The maximum speed that a ferris wheel can rotate so that the passengers remain seated on the ride (in the absence of seat belts) is .

Question 2

Which of the following statements regarding the normal force in uniform circular motion is not correct?

Answer 2

The normal force in uniform circular motion is a constant.

Question 3

The following force diagram shows a bucket containing water moving in uniform circular motion. The normal force, N, and the weight of the water, W(mg), are shown. Direction is also indicated. Which of the following equations involving the value of N is correct?

Answer 3

All of the above

Question 4

The following diagram shows a car going over a bump in the road. The bump is essentially half a circle, and its height is the radius of that circle. Which of the following statements describing the car’s impact with the bump is not correct?

Answer 4

The faster you go, the harder the bump will feel.

Question 5

The following diagrams show a guy on a Ferris wheel. The Ferris wheel has stopped with him at the top. The first diagram is a physical diagram of the guy on the Ferris wheel in motion. The second is a force diagram of the same guy. Positive direction is indicated for the force diagram. Which of the following statements regarding forces at work on the guy is correct?

Answer 5

There is the contact, or normal force, in the positive direction, and there is the force of the weight of the guy, mg, in the negative direction.

Question 6

The following force diagram shows a guy enjoying a ride on a Ferris wheel. The normal force, N, and the weight of the guy, W(mg), are shown. Direction is also indicated. Which of the following equations involving the value of N is NOT correct?

Answer 6

-N -mg = -mv^2/r

Question 7

The following diagrams show a bucket of water in uniform circular motion. Imagine swinging the bucket in a vertical circle so that none of the water leaves the bucket, even when it is directly overhead. The first diagram is a physical diagram of the bucket in motion. The second is a force diagram of the same bucket. The positive direction is indicated for the force diagram. Which of the following statements regarding forces at work on the water is correct?

Answer 7

There is the contact, or normal force, in the negative direction, and there is the force of the weight of the object, mg, in the negative direction.

Question 8

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

Answer 8

In calculating the maximum speed of a Ferris wheel, you must account for the lightest possible rider, because that rider could accidentally fly off the wheel at slower speeds than heavier riders.

Question 9

The equation for the normal force in uniform circular motion is N = mv^2/r - mg > 0
This equation can be rewritten as v > sqrt(gr)
Which of the following statements regarding this new equation is not correct?

Answer 9

None of the above