15. If both mass and velocity of a ball are tripled, the kinetic energy is incre
ID: 1628653 • Letter: 1
Question
15. If both mass and velocity of a ball are tripled, the kinetic energy is increased by a factor of: A. 3. B. 6. C. 9. D. 27. A 7.00-kg bowling ball falls from a 2.00-m shelf. Just before hitting the floor, what will be its kin energy? (g = 9.80 m/s^2 and assume air resistance is negligible) A. 14.0 J B. 19.6 J C. 29.4 J D. 137 J An amount of work equal to 1.5 J is required to compress the spring in a spring-gun. What is the "launch speed" of a 15-g marble? A. 14 m/s B. 15 m/s C. 18 m/s D. 21 m/s The area under the force vs. displacement curve represents: A. area. B. force. C. Work. D. Coefficient of static friction. Three different mass projectiles are launched from the top of a building each at different angle elevation. Each particle has the same initial kinetic energy. Which particle has the greatest kinetic just as it impacts with the ground? A. The one launched at the highest angle of elevation. B. The one with the highest mass. C. The one with the lowest mass. D. They all will have the same kinetic energy on impact.Explanation / Answer
1) Option D)
As KE = 0.5*mv^2
if m' = 3m and v' = 3v
Then KE' = 0.5*m'*v'^2 = 27*KE ======> Option D)
2) the potential energy at the top equals the kinetic energy at the moment of impact, therefore
m g h = 1/2 m v^2
and KE = 7kg*9.8m/s/s*2 J = 137.2J ========> Option D)
3) W=KE= KEf-KEi =(1/2)*m*(Vf² - Vi²)
Vf = 0
Vi=launch speed
1.5 = (1/2)*0.015*(0-Vi²)
Vi = 200 = 14 m/s (Option A)
4) Work (Option C)
Consider a situation where an object of mass, m, is lifted at constant velocity in a uniform gravitational field, g. The applied force is constant and equal to mg. If the object is lifted a distance, x, the work done by the applied force is simply mgx. A graph of Applied Force vs. Position is shown to the right. Note that the work is simply the area under the line.
5) Option D)
They all will have the same kinetic energy on impact.
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