A 3 kg block is lifted vertically 2 m by a boy in 5 sec. The work done by the bo

Question

A 3 kg block is lifted vertically 2 m by a boy in 5 sec. The work done by the boy is: Which one of the following five quantities CANNOT be used as a unit of potential energy? A). watt-second B), gram cm/s^2 c). joule D). kg m^2/s^2 E. ft middot lb A 12 kg block is released from rest 80 m above the ground. When it has fallen 40 m, its kinetic energy is: A 0.60 kg particle has a speed of 2.0 m/s at point A and a kinetic energy of 7.5 J at point B. What is the total work done on the particle as it moves from A to B? The radius of the earth is 6.38 times 10^6 m and its mass is 5.98 times 10^24 kg. What is the acceleration due to gravity at a height of 1.28 times 10^7 m above the earth's surface? What must be separation between a 5.2 kg particle and a 2.4 kg particle for their the gravitation to have a magnitude of 2.3 times 10^-12 N. An airplane flying at 200 m/s due east makes a gradual turn following a circular path to fly south. The turn takes 15 seconds to complete. What is the radius of the curve that the plane follows in making the turn?

Explanation / Answer

Work = force x displacement

W = F*d

W = mg*d

W = 3 x 9.81 x 2

W = 58.56 J

2)

B) gram-cm / s^2

3)

KE gained = PE lost = mgh = 12 kg x 9.81 m/s^2 x 40 m = 4709 Joules.

4)

KE(A) = 1/2mv^2 = 1/2 x 0.6 x 2 x 2 = 1.2 J

W = 7.5 - 1.2 = 6.3 J

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