Physics Flashcards

What is the potential energy of a 5 kg object at a height of 10 meters? (g = 10 m/s²)

Answer: 500 J

Gravitational potential energy = mgh = 5 kg × 10 m/s² × 10 m = 500 J.

Which law of thermodynamics states that energy cannot be created or destroyed?

Answer: First Law

The First Law of Thermodynamics (Law of Conservation of Energy) states that energy cannot be created or destroyed, only transformed from one form to another.

What happens to the current in a circuit if the resistance is tripled and voltage remains constant?

Answer: Current is reduced to one-third

By Ohm's Law (V = IR), if V is constant and R triples, then I = V/R becomes V/(3R), which is one-third of the original current.

What is the net force on an object moving at constant velocity?

Answer: Zero

According to Newton's First Law, an object moving at constant velocity has zero net force acting on it — all forces are balanced.

What is the focal length of a converging lens if an object at 30 cm produces an image at 15 cm?

Answer: 10 cm

Using the thin lens equation: 1/f = 1/v + 1/u = 1/15 + 1/30 = 2/30 + 1/30 = 3/30 = 1/10, so f = 10 cm.

Which electromagnetic wave has the highest frequency?

Answer: Gamma rays

In the electromagnetic spectrum, gamma rays have the highest frequency (and shortest wavelength), followed by X-rays, UV, visible light, infrared, microwaves, and radio waves.