A 3.0-kg cylinder falls vertically from rest in a very tall, evacuated tube near

Question

A 3.0-kg cylinder falls vertically from rest in a very tall, evacuated tube near the surface to the earth. What is its speed after the cylinder has fallen 6.0 m? A) 8.0 m/s B) 11 m/s C) 13 m/s D) 120 m/s E) 26 m/s 9. How much power is needed to lift a 150-kg student vertically upward at a constant speed of 0.33 m/s? A) 12.5 W B) 25 W C) 115 W D) 486 W E) 243 W 10. A 0.065-kg tennis ball moving to the right with a speed of 15 m/s is struck by a tennis racket, causing it to move to the left with a speed of 15 m/s. If the ball remains in contact with the racquet for 0.020 s, what is the magnitude of the average force exerted on the ball? A) 0 N B) 98 N C) 160 N D) 240 N E) 320 N 11. While in Earth's orbit, an 80-kg astronaut carrying a 20-kg tool kit is initially drifting toward a stationary (relative to her) space shuttle at a speed of 2 m/s. If she throws the tool kit toward the shuttle with a speed of 6 m/s as seen from the shuttle, her final speed is A) 1 m/s toward the shuttle. B) 1 m/s away from the shuttle. C) 2 m/s toward the shuttle. D) 4 m/s toward the shuttle. E) 6 m/s away from the shuttle. 12. Which one of the following is characteristic of an inelastic collision? A) Total mass is not conserved. B) Total energy is not conserved. C) Kinetic energy is not conserved. D) Linear momentum is not conserved. E) The change in momentum is less than the total impulse. 13. Three masses are positioned on a horizontal line as follows: 2.0 kg at the origin of the coordinate system, 2.0 kg at 2 meters and 4.0 kg at 5 meters. Determine the center of mass relative to the origin. A) 1.4 m B) 1.9 m C) 2.3 m D) 3.0 m

Explanation / Answer

8. using energy conservation,

mgh = m v^2 /2

v = sqrt(2 gh ) = sqrt( 2 x 9.8 x 6) = 10.8 m/s

Ans(11 m/s)

9. for constant speed, a = 0

Fnet = F - mg = 0

F = 150 x 9.8

Power = F v = (150 x 9.8) x 0.33 = 486 W

Ans(D)

10. Impulse = change in momentum = F x delat t

0.065 ( 15 + 15) = F x 0.02

F = 97.5 N

Ans(B)

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