Physics Training Test

When an object moves across a surface, the force that opposes its motion is friction. Friction is the resistance between two surfaces that are in contact. It converts kinetic energy into thermal energy, slowing the object.

At the peak of an object’s upward motion (such as a ball being thrown upward), its velocity is momentarily zero before it begins to fall back down. This is because the upward force is no longer acting, and gravity begins to pull it back down.

As a diver falls, their potential energy is converted into kinetic energy. Just before they hit the water, their speed is at its highest, meaning their kinetic energy is also at its maximum.

In a light bulb, electrical energy is converted into light energy (and some thermal energy as a byproduct). This is an example of energy transformation, where energy changes form from one type to another.

In a closed system with no external forces, the total momentum before a collision is equal to the total momentum after the collision. This is known as the principle of conservation of momentum, which applies to both elastic and inelastic collisions.

At the highest point of a pendulum’s swing, it momentarily stops before reversing direction. At this point, its kinetic energy is zero, and its gravitational potential energy is at its maximum because it is at its highest elevation relative to the lowest point of its swing.

Planets are kept in orbit around stars due to the gravitational force exerted by the star. Gravity pulls the planets toward the star, while their velocity keeps them moving forward, resulting in an orbital path.

Work is only done when a force causes a displacement. If the weight is at rest and there is no motion, no work is done. Even though energy was used to lift the object, the system does no additional work when the object is stationary.

A boat floats because of the buoyant force, which is the upward force exerted by the fluid (water) that opposes the weight of the object (the boat). When the buoyant force equals the boat's weight, the boat remains afloat.

Newton's Second Law states that the acceleration of an object is proportional to the net force acting on it and inversely proportional to its mass (F = ma). This explains why the car’s speed increases as it accelerates.