A 20 kg drum is pulled horizontally with 100 N while kinetic friction is 30 N. Its acceleration is most nearly:
- (A)3.5 m/s^2
- (B)5 m/s^2
- (C)6.5 m/s^2
- (D)70 m/s^2
Show worked solution
Answer: (A)
Net force is 70 N, so acceleration is 70/20=3.5 m/s2.
Collinear forces combine before applying Newton's second law.
Mass converts net force to acceleration.
FE Reference Handbook — Engineering Sciences: Force, Mass, and Acceleration
Why the other choices appear
- (B)Ignoring friction gives 100/20=5 m/s2.
- (C)Adding friction to applied force overstates net force.
- (D)Reporting net force as acceleration omits mass.