# Need help w/ centripetal acceleration lab questions

1. Nov 22, 2004

### ballahboy

These questions are from a lab we just did.
1. Why is an unbalanced force required to produce circular motion?

2. The ratio of squared velocity to radius is a constant. In other words, the centripetal acceleration did not change as the radius changed. Explain.

3. In an amusement park ride called the spinout, riders are positioned against the inside wall of a rotating drum. The drum begins to rotate and after a certain rotational speed is reached, the floor is lowered and the riders remain in position and do not fall. The diameter of the chamber is 4.3 meters and the period of rotation is 1.7 seconds. What is the centripetal acceleration of the rider? Approximately how many g's does the rider experience?
For this one, i got centripetal acceleration to equal 29.4m/s^2. Not sure if its correct but i don't know how to find the second part of the question.

2. Nov 22, 2004

### Sirus

Have you thought about the first two questions? Show us a little of what you have reasoned through and your process for #3.

3. Nov 22, 2004

### ballahboy

Um.. i wasnt sure about how to do #1 and 2 so i asked. And for #3 i found the velocity by using 2pi*r/t and got 7.95m/s. Then i used centripetal acc.=v^2/r and got 29.4m/s^2. Wasnt sure what the second question is asking.

4. Nov 23, 2004

### Sirus

1. When something is moving in circular motion, it is constantly changing direction. Since velocity is a vector quantity, it has both magnitude and direction. What can you, therefore, conclude about objects in circular motion?

Now also consider that $$\vec{F}_{net}=m\vec{a}$$

2. This comes from $$\vec{a}_{centripetal}=\frac{\vec{v}^{2}}{r}$$. Basically what happens is accleration doesn't change because when you change the radius the velocity changes as well, making velocity squared divided by radius a consant (acceleration).

You also know that $$\vec{F}_{centripetal}=\frac{m\vec{v}^{2}}{r}$$, and $$\vec{F}_{net}=m\vec{a}$$. Can you explain what is happening?

3. Didn't check your answer but your method looks correct. For the second part, g=9.81 m/s^2, so how many "g"s do the people experience?