In a contest, two tractors pull two identical blocks of stone the same distance over identical surfaces. However, block A is moving twice as fast as block B when it crosses the finish line. Which statement is correct?
A. Block A has twice as much kinetic energy as block B.
B. Block B has lost twice as much kinetic energy to friction as block A.
C. Block B has lost twice as much kinetic energy as block A.
D. Both blocks have had equal losses of energy to friction.
E. No energy is lost to friction because the ground has no displacement.
Answer: D
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A brass bar (E 5 110 MPa) of length L 5 2.5 m has diameter d1 5 18 mm over one-half of its length and diameter d2 5 12 mm over the other half. Compare this nonprismatic bar to a prismatic bar of the same volume of material with constant diameter d and length L. The elon-gation of the prismatic bar under the same load P 5 25 kN is approxi-mately:
(A) 3 mm
(B) 4 mm
(C) 5 mm
(D) 6 mm
A 20-mF capacitor is attached across a 1000-V power supply. What is the net charge on the capacitor?
a. 20 mC c. 10 mC b. 40 mC d. none of these choices
An object is thrown upwards with a speed of 16 m/s. How long does it take it to reach a height of 7.0 m on the way up? Neglect air resistance
A) 0.52 s B) 1.2 s C) 2.4 s D) 3.1 s E) 4.2 s
Consider a situation where you carry a 20 N box up a flight of stairs, raising its elevation by 5 m. The increase of potential energy of the box is
a. 0 c. 100 J b. 4 J d. none of the above