ECAT MCQs

Opposing forces subtract.
Net force = 50-20 = 30 N.

Internal forces cancel in pairs within a system.
With no net external impulse, total momentum remains constant.

Use a=F/m.
A=12/4 = 3 m/s².

All isolated collisions conserve momentum.
Elastic collisions also conserve total kinetic energy.

Centripetal force is mv²/r.
F=2×36/4 = 18 N.

The objects share a common final velocity.
Momentum is conserved, but kinetic energy is not.

Centripetal acceleration is v²/r.
A=100/20 = 5 m/s².

Acceleration is F/m = 4 m/s².
Change in velocity is at=4×3 = 12 m/s.

The net force is 80-20 = 60 N.
Acceleration is 60/15 = 4 m/s².

Constant velocity means zero acceleration and zero net force.
The normal force therefore equals the person's weight, 600 N.

Work transfers energy when a force acts through a displacement.
Only the component of force along displacement contributes.

Kinetic energy depends on mass and speed.
For translational motion, K=½mv².