A girl and her bicycle have a total mass of 46.0 kg. At the top of the hill her speed is 6.0 m/s, and her speed doubles as she rides down the hill. The hill is 15.0 m high and 105 m long. How much kinetic energy and potential energy is lost to friction?
a. 4.3E+3 J
b. 7.6E+3 J
c. 3.5E+3 J
d. 4.4E+3 J
e. 4.2E+3 J
a
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Fred swings a sheet of copper in pendulum fashion between the poles of a strong magnet. The sheet slows in entering the magnetic field because the field
A) induces swirling currents in the copper and accompanying magnetic fields that resist motion. B) experiences both air and magnetic friction. C) is repelled by free electrons in the copper. D) none of the above
Two children seat themselves on a seesaw. The one on the left has a weight of 300 N while the one on the right weighs 200 N. The fulcrum is at the midpoint of the seesaw. If the child on the right is not at the end but is 1.50 m from the fulcrum and the seesaw is balanced, what is the torque provided by the weight of the child on the left? (Take ccw as positive.)
a. –300 N·m b. 300 N·m c. 450 N·m d. –450 N·m e. 150 N·m
A ball rolls across a floor with an acceleration of 0.10 m/s2 in a direction opposite to its velocity. The ball has a velocity of 4.00 m/s after rolling a distance 6.00 m across the floor. What was the initial speed of the ball?
A) 4.15 m/s B) 5.85 m/s C) 4.60 m/s D) 5.21 m/s E) 3.85 m/s
A satellite orbits just above the Earth's surface. (a) Calculate the period of the satellite. (b) Calculate the speed of the satellite
What will be an ideal response?