# Centripetal Force Experiment. Measure the centripetal force and compare it with the theorectical value Fc=mr&#969;2

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Introduction

AL Physics TAS 1

Centripetal Force

(2008/11/12)

1. Objective

To measure the centripetal force and compare it with the theorectical value Fc=mrω2

2. Theory

Consider an rubber bung moving with constant angular speed in a circular path,

where θ is angle between string and vertical,

T is tension in the string,

m is mass of rubber bung,

g is acceleration due to gravity,

L is length of string,

r is the radius of circular path, and

ω is the angular speed of bung.

Theorectically, Mg=T= mω2L, where M is mass of weights used.

3. Method

Refer to the figure in the worksheet.

Middle

1.39

0.800

0.1400

1.37

12.03

12.66

12.35

10.1

1.59

0.750

0.1600

1.57

12.92

13.06

12.99

9.67

1.35

0.750

0.1800

1.77

11.75

11.72

11.74

10.7

1.65

Table 1

5. Errors and Accuracy

After calculations, the fractional errors are summarized as follow:

= ±2.60×10-3

M / kg (±5×10-5) | L / m (±5×10-4) | t |

Conclusion

## Precautions

- The rubber bung was tied securely and is whirled safely without hitting any person or object.
- Swith off the fan for more accurate measurment of mass.

## Comparison of Experimental with Expected Result

Refer to Table 1, for M=0.1, 0.16 and 0.18, tension (mω2L) is smaller thanMg. For M=0.12 and 0.14, tension is larger than Mg.

Apart from errors, the main source of such difference is friction between glass tube and string.

Friction can act on the string either upward (when ω slightly decrease) or downward (when ω slightly increase).

For M=0.1, 0.16 and 0.18, friction act upward.

For M=0.12 and 0.14, friction act downward.

7. Conclusion

Taking the errors into account, Fc=mrω2 is verified.

~ End ~

P.

AL-PHY-TAS 1

This student written piece of work is one of many that can be found in our AS and A Level Fields & Forces section.

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