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Physics
Test #4
Name:
1. A planet has 5x the earth's mass and 10x its radius. What would "g" be on this planet?
2. A moon is located 6.55 x 10^8 m from a planet. Determine the mass of the planet if it takes 2.91 days for the moon to orbit the planet.
3. A coin is 15 cm from the center of a turntable. What must the coefficient of friction to hold the penny in place if the turn table rotates
once every 1.33 secs?
4. a) Diagram the forces that acted on the airplanes in my airplane swing; explain what provides the
centripetal force.
b) If the planes have a mass of 60g and travel in a circle of radius 20 cm at a speed of 30 cm/sec what angle do they make with the vertical?
5. A ferris wheel whose radius is 10.0 m rotates once every 80 secs. A 65 kg student rides. What is the Normal force at
a) the top and
b) bottom
c) diagram the forces at the top
6. a) State and explain Kepler's 2nd Law
b) The period of planet Barbie is .62 years and that of planet Cornelius is 1.9 years. Which plant is closest to the Sun:Barbie, Earth or
Cornelius?
7. What is the minimum velocity to keep the marble at the top of the vertical loop on track if the radius is 20 cm?
b) If the marble moves faster than this velocity what forces make it go in a circle?
8. What force is needed to make a 10 kg mass go at 10 m/sec in a circle of radius 10m?
Part II.
1.
2.
3.
4.
What does the word “centripetal” mean?
What are the units of centripetal force? Centipetal acceleration?
Is an object going in a circle at constant speed accelerating? Explain.
In the centriopetal force lab, you rotated a mass in a dfairly horizontal circle. If you double the speed of rotation, what did you have
to do the hanging mass? Increase/decrease and by what factor.
5. Explain why you don’t need a horse collar to hold you in at the top of the vertical loop.
Bonus A stone, of mass m, is attached to a strong string and whirled in a vertical circle of radius r. At the exact top of the path the tension in
the string is 3 times the stone's weight. The stone's speed at this point equals _________?
B2: Using a diagram and words show the forces that enable a car to take an exit ramp curve.