A block rests on a frictionless horizontal track and is attached to a light spring…
PHYSICS · Multi-part · AP · Physics 1: Algebra-based · Force and Translational Dynamics · Force and Translational Dynamics
Problem
A 0.50kg block rests on a frictionless horizontal track and is attached to a light spring fixed to a wall. The equilibrium position of the block–spring system is defined to be x=0. A coordinate axis is chosen so that displacements to the right are positive.
The block is pulled 0.10m to the left (so x=−0.10m) and released from rest. Assume air resistance is negligible.
(a) While the block is still at x=−0.10m, state the direction (left or right) of the force the spring exerts on the block. Give your answer relative to the positive x-axis defined above.
(b) After release, the block moves through the equilibrium point and reaches x=+0.05m moving rightward. At that instant, indicate the direction of the spring’s force and explain how the sign of the block’s displacement is related to this direction.
(c) A student claims that the mathematical expression for the spring force must include a negative sign. Using the situations described in parts (a) and (b), provide a qualitative argument that supports or refutes the student’s claim without writing the explicit formula.