A 2 kg block is lifted by 5 m. What work is done against gravity?

A 2 kg block is lifted by 5 m. What work is done against gravity?

• A. 8 J
• B. 49 J
• C. 0 J
• D. 98 J

Answer: (D)

Work against gravity equals the increase in gravitational potential energy, so W = m g h. With a mass of 2 kg lifted 5 m, this is W = 2 × 9.8 × 5 ≈ 98 joules. This is the energy you must provide to raise the block, stored as gravitational potential energy. (The work gravity does would be the opposite sign, −98 J, since gravity acts downward while the block moves upward.)

Work against gravity equals the increase in gravitational potential energy, so W = m g h. With a mass of 2 kg lifted 5 m, this is W = 2 × 9.8 × 5 ≈ 98 joules. This is the energy you must provide to raise the block, stored as gravitational potential energy. (The work gravity does would be the opposite sign, −98 J, since gravity acts downward while the block moves upward.)