Samples Physics Centripetal Force Prelab Questions

# Centripetal Force Prelab Questions

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1) Define “centripetal force”. How is it related to “centrifugal force”?
Centripetal force is the force that keeps objects moving at a uniform speed along a circular path. This is directed along a circle’s radius, towards the center of the circle away from the object. Centrifugal force is the lack of centripetal force; it is not a true force but an inertia of motion. It describes the tendency of an object traveling along a curved path to fly off from the center of curvature.

2) If you count 70 rotations of some system in 60 seconds, what is the frequency of rotation? What is the angular frequency? What is the period of the rotation?
Freq = 1/period = 1/(60/70)= 1.166667 Hz
Angular frequency = ω = 2πf = 5.385569 rad/s
Period of rotation = 60/70 = 0.854143s

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3) What provides the centripetal force in this lab? Describe what happens.
The weights on the bottom of the string provide the centripetal force, pulling the object towards the middle of the tube, or the center of the radius, which increases when the angular velocity is increased.

4) Recall that the International Space Station (ISS) orbits at a height of about 430km above the surface of the Earth. Using the law of gravity and the formula for centripetal force, show how to calculate its orbital velocity.
Fc = (m1v^2)/r where m=mass of object
(Gm1m2)/r^2 = (m1v^2)/r
v = sqrt(Gm2)/r) Where G is 6.67 x10^-11Nm^2/kg^2 – m2=mass of earth r=radius
r=430000+(6.38×10^6) = 6.8 x10^6 (to earth center)
v= sqrt((6.67×10^-11*5.972×10^24)/6.8×10^6) =7653.645806 m/s

5) If the ISS were orbiting the Moon at same height above the surface, would it be going at a faster, slower, or the same velocity? Explain.
Slower. Due to fact the moon’s mass is less, and radius is less (when measured from center of planet).