Answer to Question #323959 in Classical Mechanics for Mathan

Question

A child is dragging a small crate across the horizontal floor as shown in the figure above. She is dragging the crate using a string such that the tension force in the string is 20 N.

If the crate has a mass of 9.2 kg and is accelerating at a rate of 0.55 m s⁻² then what is the magnitude of the friction force on the crate from the floor? (to 2 s.f)

Answer 1

$ma=F-F_{fr},$

$F_{fr}=F-ma=15~N.$