Two object with m_1 and m_2 have the Same kinetic energy and are both moving 4m_

Question

Two object with m_1 and m_2 have the Same kinetic energy and are both moving 4m_2. the ratio of the stopping of m_1 to that of m_2 is: 1:4 4:1 1:2 2:1 1:1 A 5.0-kg cart is moving horizontally at 6.0 m/s. In order to change its speed to 10.0 m/s. the net work done on the cart must be: 40 J 90 J 160J 400J 550J The work done by gravity during the descent of a projectile is: positive negative zero depends for its sign on the direction of the y axis depends for its sign on the direction of both the x and y axes A woman lifts a barbell 2.0 m in 5.0 s. If she lifts it the same distance in 10 s. the work done by her is: four times as great two times as great the same half as great one-fourth as great A 1.5 kg crate falls from a height of 2.0 m onto an industrial spring scale with a spring constant of 1.5 times 10^5 N/m. At its greatest compression the reading on the scale is: 15 N 30 N 1.5 times 10^3 N 2.1 times 10^3 N 3.0 times 10^3 N

Explanation / Answer

17.

work done = change in KE = (0.5) m (Vf2 - Vi2) = (0.5) (5) (102 - 62) = 160 J

18.

W = F .d

during decent , F and d   are in same direction . hence W is positive

19.

work done in 5 sec = , W1 = mg(2) /5

work done in 10 sec = , W2 = mg(2) /10

W2 /W1 = 1/2

so half as great

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