If the voltage across a circuit of constant resistance is doubled, the power dissipated by that circuit will
A) be four times as large.
B) be two times as large.
C) decrease to one-half the original power.
D) decrease to one-fourth the original power.
A
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Mary and Debra stand on a snow-covered roof. They both throw snowballs with the same initial speed, but in different directions. Mary throws her snowball downward, at 30° below the horizontal; Debra throws her snowball upward, at 30°
When the snowballs reach the ground below, A) Debra's snowball will have a higher speed than Mary's. B) Mary's snowball will have a higher speed than Debra's. C) Both snowballs will hit the ground with the same speed. D) Debra's snowball never hits the ground since it is thrown upwards. E) Mary's snowball never hits the ground since it is thrown downwards.
Two masses m1 and m2, with m1 = 3 m2, undergo a head-on elastic collision. If the particles were approaching with speed v before the collision, with what speed are they moving apart after collision?
a. v c. 3v/4 b. v/3 d. 3v
A child throws a ball with an initial speed of 8.00 m/s at an angle of 40.0° above the horizontal. The ball leaves her hand 1.00 m above the ground. How long is the ball in flight before it hits the ground?
A) 1.22 s B) 6.79 s C) 7.45 s D) 9.14 s E) 2.44 s
A small block of mass m can slide along the frictionless loop-theloop. The block is released from rest at point P, at height h = 5R above the bottom of the loop. How much work does the gravitational force do on the block as the block travels from point P to
(a) point Q and
(b) the top of the loop?
If the gravitational potential energy of the block–Earth system is taken to be zero at the bottom of the loop, what is that potential energy when the block is
(c) at point P,
(d) at point Q, and
(e) at the top of the loop?
(f) If, instead of being released, the block is given some initial speed downward along the track, do the answers to (a) through (e) increase, decrease, or remain the same?