A 2 kg block is lifted vertically by 3 meters. What is the work done by gravity on the block?

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Multiple Choice

A 2 kg block is lifted vertically by 3 meters. What is the work done by gravity on the block?

Explanation:
Gravity does negative work when you lift an object upward, because the force of gravity points downward while the displacement is upward. The work is W = F · d = (m g) × 3 m with a minus sign since the force and displacement are opposite, giving W = - m g h = - (2 kg)(9.8 m/s^2)(3 m) = -58.8 J. This also reflects the increase in gravitational potential energy by 58.8 J when the block is raised, so gravity does an amount of work equal in magnitude and opposite in sign. Hence the work done by gravity is -58.8 J.

Gravity does negative work when you lift an object upward, because the force of gravity points downward while the displacement is upward. The work is W = F · d = (m g) × 3 m with a minus sign since the force and displacement are opposite, giving W = - m g h = - (2 kg)(9.8 m/s^2)(3 m) = -58.8 J. This also reflects the increase in gravitational potential energy by 58.8 J when the block is raised, so gravity does an amount of work equal in magnitude and opposite in sign. Hence the work done by gravity is -58.8 J.

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