A 5kg rock and a 10kg rock are dropped from a height of 10m. Which of the following statements describes what happens to the potential energy of the rocks?
a) Neither rock loses potential energy because no work is done on the rocks.
b) Bother rocks lose the same amount of potential energy because they fall from the same height.
c) The 10kg rock loses more potential energy than the 5kg rock because the 10kg rock falls faster.
d) The 10kg rock loses more potential energy than the 5kg rock because the 10kg rock has more mass.
Answer: d) The 10kg rock loses more potential energy than the 5kg rock because the 10kg rock has more mass.
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Which of the following statements about scientific models is true?
What will be an ideal response?
In order to get an object moving, you must push harder on it than it pushes back on you
A) True B) False
A box slides down a frictionless incline, and a hoop rolls down another incline. Both inclines have the same height, and both the box and the hoop have the same mass. If both objects start from rest, upon reaching the bottom of the incline which one will have the greater kinetic energy and which one will have the greater speed?
a. The box will have both the greater kinetic energy and the greater speed. b. The hoop will have both the greater kinetic energy and the greater speed. c. Both will have the same kinetic energy, but the hoop will have the greater speed. d. Both will have the same kinetic energy, but the box will have the greater speed.
Radiation: A blacksmith is flattening a steel plate having dimensions 10 cm × 15 cm × 1 mm. He has heated the plate to 900 K. If the emissivity of the plate is 0.75, at what rate does it lose energy by radiation? Ignore any heat exchange with the surroundings. (? = 5.67 × 10-8 W/m2 ? K4)
A. 360 W B. 760 W C. 790 W D. 850 W E. 880 W