A student whose mass is stands at rest on a frictionless skateboard facing a rigid…
PHYSICS · Multi-part · CBSE · Physics · Laws of Motion · Laws of Motion
Problem
A student whose mass is 60kg stands at rest on a frictionless skateboard facing a rigid brick wall. The student extends her arms and pushes horizontally on the wall for 0.20s. A motion sensor attached to her hand records that the horizontal force exerted on the wall is constant at 120N during the push and drops to zero immediately afterward. Friction with the ground and air resistance are negligible.
(1) Part 1: Identify the pair of interaction forces between the student and the wall, clearly stating the agent and the object for each force.
(2) Part 2: Describe (in words or with a sketch) a complete free-body diagram for the student during the 0.20s interval while she is in contact with the wall.
(3) Part 3: Determine the magnitude of the student’s horizontal acceleration while the force on the wall is non-zero.
(4) Part 4: Explain why the wall does not move appreciably even though it experiences a 120N horizontal force.
(5) Part 5: Using the concept of defining a system, explain why the forces you identified in part (a) do not cancel when predicting the subsequent motion of the student on the skateboard.