Physics Mechanics 4

Question 1

A satellite orbits Earth in a circular orbit. Which force provides the centripetal acceleration?

Accepted Answer

Gravity from Earth

Answer

Earth's gravity continuously pulls the satellite toward Earth's center, providing the centripetal force needed for circular orbit.

Question 2

A 4 kg object moves in a horizontal circle of radius 2 m at a speed of 3 m/s. What is the centripetal force acting on it?

Accepted Answer

18 N

Answer

Centripetal force = mv²/r = 4 × 9 / 2 = 18 N.

Question 3

What happens to the period of a simple pendulum if its length is quadrupled?

Accepted Answer

It doubles

Answer

Period T = 2π√(L/g); quadrupling L multiplies T by √4 = 2, so the period doubles.

Question 4

A 1500 kg car traveling at 30 m/s brakes to a stop. How much work does friction do on the car?

Accepted Answer

−675,000 J

Answer

Work done by friction = ΔKE = 0 − ½(1500)(30²) = −675,000 J; friction removes kinetic energy.

Question 5

Two identical balls collide head-on elastically with equal speeds. What happens after the collision?

Accepted Answer

Both balls rebound with their original speeds reversed

Answer

In a perfectly elastic head-on collision of equal masses, the balls exchange velocities, each rebounding at its original speed.

Physics Practice Test