# Online Physics Assignment Help – Hybrid Assignment: Rotation

## Online Physics Assignment Help

### Hybrid Assignment: Rotation

PHYS 153 NAME:

Hybrid Assignment: Rotation

Due Date: Thursday, March 31, 2016, at the beginning of class

You may print this sheet and write your answers on it, or write your answers on separate pages (be sure to clearly label each question

Open a web browser, and navigate to the following web page:

http://serc.carleton.edu/student_videos/index.html#rotation

Look for the video called “Bicycle Wheel Accelerated By Weight.” Click the DMV link and start the video.

You should see a frame like Figure 1 below:

Figure 1: Screenshot using DMV player

Using the video controls, you can advance the video one frame at a time. Note the scales marked on the screen

for measuring position. Using the data available on-screen, answer the following questions. Where calculations

are necessary, show your steps on this page or attach extra pages. When counting frames, round to the nearest

frame (e.g. 2.5 frames would be rounded up to 3 frames). We will be working with many approximations.

Play the entire video completely before you begin, then reset before you answer the following questions.

1. What is the frame rate for the video?

2. Suppose an event on the video takes 10 frames to happen. How many seconds did the event take? (Show

the steps in your calculation below)

3. What is the frame number when the red string is cut (the wheel is released)?

4. What is the radius of the wheel (i.e. the distance from the axle to the outer edge of the wheel)?

5. Suppose the metal object pulling on the left edge of the wheel has mass 500 grams. What is the weight of

this object in Newtons?

6. How much torque is caused by the hanging weight?

7. Notice that the torque due to the falling weight causes the wheel to have angular acceleration. Write

Newton’s Second Law for rotation (the equation that connects torque and angular acceleration):

8. If we model the wheel as a hoop (or hollow cylinder), what is the formula we would use to calculate the

rotational inertia of the wheel (see Section 8.1)?

9. Notice that, as the mass falls, its gravitational energy decreases. Let’s consider the system consisting of the

falling mass, the Earth, and the wheel. Let’s also suppose that there is some friction as the wheel turns. If the

gravitational energy decreases, what type(s) of energy increase in the video?

10. Consider a similar situation, with some different data:

A flywheel of mass 182 kg has an effective radius of 0.62 m (assume the mass is concentrated along a circumference

located at the effective radius of the flywheel).

(a) What torque is required to bring this wheel from rest to a speed of 120 rpm in a time interval of 30.0 s?

(b) How much kinetic energy is gained by the wheel?
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