Work, Energy, and Power Flashcards

How much work is done when a force of 50 N moves an object 8 meters in the direction of the force?

Answer: 400 J

Work = Force × Distance = 50 N × 8 m = 400 Joules. Work is only done when the force has a component in the direction of motion.

A 2 kg ball is moving at 6 m/s. What is its kinetic energy?

Answer: 36 J

Kinetic Energy = ½mv² = ½ × 2 × (6)² = ½ × 2 × 36 = 36 J.

An object with a mass of 5 kg is lifted 3 meters above the ground. What is its gravitational potential energy? (g = 10 m/s²)

Answer: 150 J

Potential Energy = mgh = 5 kg × 10 m/s² × 3 m = 150 J.

A machine does 500 J of work in 10 seconds. What is its power output?

Answer: 50 W

Power = Work / Time = 500 J / 10 s = 50 Watts. Power measures the rate at which work is done.

According to the work-energy theorem, if a net force does 200 J of work on an object, what happens to the object's kinetic energy?

Answer: It increases by 200 J

The work-energy theorem states that net work done on an object equals the change in its kinetic energy. Positive net work increases kinetic energy.

A 10 kg object falls from a height of 5 m. Ignoring air resistance, what is its kinetic energy just before it hits the ground? (g = 10 m/s²)

Answer: 500 J

All potential energy converts to kinetic energy: KE = mgh = 10 × 10 × 5 = 500 J. This demonstrates conservation of mechanical energy.