PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A 4.0kg crate rests on a level loading dock. Kinetic friction between the crate and the dock is 10N acting opposite any horizontal motion.
A worker first pulls the crate to the right with a steady horizontal force of 10N. After the crate has moved several centimeters at constant speed, a coworker suddenly adds an additional horizontal force of 1.5N to the right, so that the two pulling forces act together.
(1) Before the coworker’s force is applied, determine the net horizontal force on the crate and state whether the forces are balanced or unbalanced.
(2) After the coworker’s force begins acting, determine the new net horizontal force on the crate.
(3) Calculate the crate’s magnitude of horizontal acceleration once both pulling forces are applied.
(4) Explain qualitatively how the crate’s motion is expected to change after the additional 1.5N force is applied, comparing it to its motion just before that instant.