You push a crate with 40 N of force across 3 meters of floor. How much work do you do?
A13.3 J
B43 J
C120 J
D40 J
Work = Force × Distance = 40 N × 3 m = 120 J.
Question 2 True / False
Holding a heavy suitcase while standing still counts as doing work in physics.
TTrue
FFalse
Answer: False
Work requires movement in the direction of the force. If the suitcase does not move, no work is done on it, even though your muscles are exerting force.
Question 3 Short Answer
Why does friction do negative work on a sliding object?
Think about your answer, then reveal below.
Model answer: Because friction acts in the opposite direction to the object's motion, removing kinetic energy rather than adding it.
Work is negative when the force opposes the direction of motion. Friction always opposes sliding, so it always does negative work on the moving object.