Centripetal Force

Centripetal Force

Purpose: To verify Newton’s second law of motion for the case of uniform circular

motion.

Equipment:

Centripetal force apparatus                               metric scale

vernier caliper                                                   stop watch

slotted weight set                                            weight hanger

 triple beam balance

Introduction:

The centripetal force apparatus is designed to rotate a known mass trough

a circular path of known radius. By timing the motion for a definite

number of revolutions and knowing the total distance that the mass has

traveled, the velocity can be calculated. Thus the centripetal force, F,

necessary to cause the mass to follow its circular path can be

determined from Newton’s second law.

F= (mv^(2))/r

Where m is the mass, v is the velocity, and r is the radius of the circular

path.

Here we have used the fact that for uniform circular motion, the

acceleration, a, is given by: a=(v^2)/r

Procedure:

1. For each trial we position of the horizontal crossarm and the vertical indicator

post must be such that the mass hangs freely over the post when the spring is

detached. After making this adjustment, we connect the spring to the mass and

practice aligning the bottom of the hanging mass with the indicator post while

rotating the assembly.

2. We measured the time for 50 revolutions of the apparatus. Keep the velocity as

constant as possible by keeping the pointer on the bottom of the mass aligned with

the indicator post. We placed a white sheet of paper as a background behind the

apparatus that was helpful in getting the alignment as close as possible. Using the

same mass and radius ,we measure the time for three different trials. Record all data

in a neat excel table as shown below.

3. Using the average time obtained above, calculate the velocity of the mass. From

this calculate the centripetal force exerted on the mass during its motion.

4. We determine the centripetal force by attaching a hanging weight to

the mass until it once again is positioned over the indicator post this time at rest.

Since the spring is being stretched by the same amount as when the apparatus was

rotating, the force stretching the spring should be the same in each case.

5. We then calculated the centripetal force as shown below.

• Conclusions:

o What did you learn? I learned how to calculate centripetal force of an object moving in an circular motion and also learned how to calculate the velocity of an object in centripetal motion.

o Discuss possible sources of error. Possible sources of error might include our constant velocity of while rotating. And also the spring’s movement was radical moving to much or to little.

o Can you think of ways to redesign/improve this lab? Maybe finding a way to keep constant velocity actually constant.