A laboratory cart of mass 4.0 kg rests on a horizontal track assumed to be frictionless
PHYSICS · Multi-part · CBSE · Physics · Force and Laws of Motion · Force and Laws of Motion
Problem
A laboratory cart of mass 4.0 kg rests on a horizontal track assumed to be frictionless. Two thin strings are attached to the cart and run parallel to the track. Student A pulls one string toward the +x direction with a constant force of 15 N, while Student B simultaneously pulls the other string toward the –x direction with a constant force of 10 N.
Answer the following in the order given, showing all reasoning and using correct physics terminology.
(a) Draw a clearly labeled free-body diagram for the cart. Identify each external force acting on the cart and label its direction.
(b) Using your diagram, determine the numerical value (including sign) of the net external force acting on the cart along the track.
(c) Describe, without performing any further calculation, the direction of the cart’s acceleration and explain your reasoning in one or two complete sentences.
(d) Suppose a second identical cart is rigidly attached to the first so that their combined mass is 8.0 kg while the two students continue to pull with the same forces. Qualitatively compare the new acceleration to that found in part (b) and justify your answer using Newton’s laws.