Question

an object is moving. the forces acting on it are obscured.
without more information, what do we know for sure about the object?
choose 1 answer:
a the objects speed must change.
b the objects direction of motion must change.
c both the objects speed and direction of motion must change.
d either the objects speed or direction of motion must change. possibly both will change.

Explanation:

When forces on an object are unbalanced, the object accelerates. Acceleration means a change in velocity, and velocity has two components: speed (magnitude) and direction. So either speed, direction, or both must change. Option A is wrong because direction could change while speed stays same (e.g., uniform circular motion). Option B is wrong as speed could change while direction stays same (e.g., linear acceleration). Option C is wrong as only one component (speed or direction) could change, not necessarily both. Option D correctly states that either speed, direction, or both must change.

Answer:

D. Either the object’s speed or direction of motion must change. Possibly both will change.