IB Physics SL A.2.2 Forces as Interactions Between Bodies

Practise identifying which bodies exert each force, distinguishing internal from external interactions and using the resultant external force to explain a system's acceleration.

Syllabus
First assessment 2025
Objective
—
Level
SL

Exam points

  • name both interacting bodies for weight, normal reaction, tension or contact forces instead of naming an effect
  • exclude internal action-reaction forces when finding the resultant force on a combined system
  • relate a non-zero resultant external force to acceleration rather than assuming opposing forces are equal

A.2.2—Forces as interactions between bodies question 1

[Maximum number: 1]

An elevator (lift) and its load accelerate vertically upwards.

Figure for Question A.2.2—Forces as interactions between bodies question 1 — IB Physics SL

Which statement is correct in this situation?

A

The net force on the load is zero.

B

The tension in the cable is equal but opposite to the combined weight of the elevator and its load.

C

The normal reaction force on the load is equal but opposite to the force on the elevator from the load.

D

The elevator and its load are in translational equilibrium.

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