Question Detail

PHY 101 Work, Energy and Power Objective Question
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Question

What is the work done by the gravitational force on an object of mass m moving vertically from y_i to y_f?
Options
A W_g = mg(y_f - y_i)
B W_g = -mg(y_f - y_i)
Correct Answer
C W_g = ½ m(v_f² - v_i²)
D W_g = 0
Correct Answer

Option B is the correct answer.

Detailed Explanation

The work done by gravity is W_g = FΔy cos θ. The force is downward (mg) and the angle between force and displacement is 0° if moving down, 180° if moving up. This leads to W_g = -mg(y_f - y_i). Alternatively, W_g = PE_i - PE_f.

Hint

Gravity does positive work when an object falls, negative work when it rises.

Question Info

Course: PHY 101
Topic: Work, Energy and Power
Type: Objective
Difficulty: Not specified
Question 389 of 1250
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