Physics Mechanics Flashcards

Two forces of 3 N and 4 N act at right angles to each other. What is the magnitude of the resultant force?

Answer: 5 N

Using Pythagoras: R = √(3² + 4²) = √(9 + 16) = √25 = 5 N. This is the classic 3-4-5 right triangle.

An object moves in a circle at constant speed. In which direction does the centripetal acceleration act?

Answer: Towards the centre of the circle

Centripetal acceleration always acts towards the centre of the circular path. It continuously changes the direction of velocity without changing its magnitude, keeping the object moving in a circle.

A spring with spring constant k = 200 N/m is compressed by 0.15 m. What is the elastic potential energy stored?

Answer: 2.25 J

Elastic PE = ½kx² = ½ × 200 × 0.15² = ½ × 200 × 0.0225 = 2.25 J.

What is the principle of conservation of momentum?

Answer: The total momentum of a closed system remains constant provided no external resultant force acts

The principle states that in a closed system (no external resultant force), total momentum before an event equals total momentum after. This applies to all collisions and explosions.

A 0.5 kg ball moving at 6 m/s collides with a stationary 1.5 kg ball. They stick together. What is their velocity after the collision?

Answer: 1.5 m/s

Using conservation of momentum: (0.5 × 6) + (1.5 × 0) = (0.5 + 1.5) × v. So 3 = 2v, giving v = 1.5 m/s. This is a perfectly inelastic collision.

On a velocity-time graph, what does the area under the line represent?

Answer: Displacement

The area under a velocity-time graph gives the displacement of the object. This is because displacement = velocity × time, which corresponds to the area calculation. Areas below the time axis represent displacement in the negative direction.