LAB: CENTRIPETAL FORCE PHYSICS

Name: ____________________________
LAB: CENTRIPETAL FORCE
PHYSICS - TALBOO
Date: ______________ Period: ________
OBJECTIVE
Students will investigate the relationship between centripetal force,
velocity and radius for a revolving rubber stopper.
MATERIALS
-
Stopwatch
Metal tube
Calibrated mass set
Calculator
- Nylon string
- Rubber stopper with hole
- Paper clip
PROCEDURE
1.
Thread the free end of the string through the metal tube. The length of string between
the rubber stopper and the handle should be 0.5 meter (marked in red line on your string).
2. Hold the free end of the string firmly in one hand and the metal tube in the other. Make
sure you have an area clear of other students. Begin to swing the stopper slowly in a
horizontal circle overhead.
a. Feel the pull on the string as the speed of the stopper increases. As the speed of
the stopper increases, does the pull on the string increase or decrease?
b. Try swinging the rubber stopper at a constant speed and slowly let some string out
to increase the radius of the circle. How does the force on the string change?
3. Return the string to its original half-meter length. Tie a loop in the free end of the string
and hook the paperclip to it.
4. Hook a mass on the end of the paper clip. Convert this mass into weight and record this
value in the data table.
5. Slowly begin to swing the rubber stopper overhead. Increase or decrease the speed of
rotation until the red line is lined up with the top of the metal tube.
6. The centripetal force and the hanging weight are equal when the red line is stationary at
the top of the metal tube.
7. Find the period (T) of the rubber stopper by timing 20 revolutions and then dividing by
20. Record this value in the data table.
8. Find the rubber stopper’s velocity (v) by v = 2πr / T where r = 0.5 m. Record this value
in the data table.
9. Calculate v2 and record this value in the data table.
10. Add an additional 50 g to the paper clip and repeat steps 5 – 9.
DATA
Mass (g)
Weight = Centripetal Force (N)
0
0
50
100
150
200
250
300
350
T (s)
v (m/s)
v2 (m2/s2)
0
0
ANALYSIS
1.
Make a graph of centripetal force vs. velocity and a graph of centripetal force vs. v2.
2.
The graph that better approximates a straight line represents the relationship between
force and velocity. Which graph better approximates a straight line? Draw a best fit line
on that graph.
3.
According to your graphs, is force dependent of velocity or velocity squared?
4.
What will happen to the centripetal force acting on an object if its velocity is doubled?
5. If your radius doubled, what would need to happen to your centripetal force? (assume
constant velocity and mass)
6.
If your radius increased, what would need to happen to your velocity? (assume constant
centripetal force and mass)