602 Scientific Principles Area 3, 4 & 5

What is force?

• A push or pull acting on an object

• The ability to do work

• The speed of an object in motion

• The resistance of an object to motion

Answer explanation

Force is defined as a push or pull acting on an object, making it the correct choice. It is the fundamental concept that describes how objects interact and change their motion.

Newton’s Second Law states that force is equal to:

• Mass x Velocity

• Mass x Acceleration

• Work ÷ Time

• Energy ÷ Distance

Answer explanation

Newton’s Second Law states that force equals mass times acceleration (F = ma). This means the correct choice is 'Mass x Acceleration', as it directly relates force to the mass of an object and its acceleration.

Which of the following best defines "work" in physics?

• The force applied to an object

• The energy transferred when a force moves an object

• The speed at which a force is applied

• The resistance an object experiences when moving

Answer explanation

In physics, 'work' is defined as the energy transferred when a force moves an object. This means that work involves both the application of force and the movement of the object in the direction of that force.

Which of these is an example of kinetic energy?

• A stretched rubber band

• A book sitting on a shelf

• A moving car

• A compressed spring

Answer explanation

Kinetic energy is the energy of motion. A moving car is an example of kinetic energy because it is in motion, while the other options (stretched rubber band, book on a shelf, compressed spring) represent potential energy.

What must be true for mechanical energy to be conserved?

• Only kinetic energy is present

• There are no external forces like friction

• Work is not being done

• Energy is lost in the form of heat

Answer explanation

For mechanical energy to be conserved, there must be no external forces like friction acting on the system. Friction converts mechanical energy into heat, preventing conservation.

The work-energy theorem states that:

• Work is equal to the change in kinetic energy

• Work is equal to mass times acceleration

• Energy is always lost when work is done

• Power is the rate at which work is done

Answer explanation

The work-energy theorem states that work done on an object results in a change in its kinetic energy. Therefore, the correct choice is that work is equal to the change in kinetic energy.

Power is defined as:

• Work divided by time

• Force multiplied by distance

• Energy stored in an object

• The force required to lift an object

Answer explanation

Power is defined as the rate at which work is done, which is calculated by dividing work by time. Therefore, the correct answer is 'Work divided by time'.

Which of the following is an example of an efficient machine?

• A machine that loses most of its energy as heat

• A device that uses minimal energy to do maximum work

• A system where energy is constantly lost

• A machine that stops working after a short time

Answer explanation

An efficient machine is one that maximizes output while minimizing energy input. The correct choice, 'A device that uses minimal energy to do maximum work', exemplifies this principle, unlike the other options that indicate energy loss.

If a person pushes a box with a force of 50 N over a distance of 5 meters, how much work is done?

• 10 J

• 250 J

• 500 J

• 1250 J

Answer explanation

Work is calculated using the formula: Work = Force × Distance. Here, Work = 50 N × 5 m = 250 J. Therefore, the correct answer is 250 J.

A motorcycle engine generates 500 watts of power. How much work does it do in 10 seconds?

• 50 J

• 500 J

Answer explanation

Power is the rate of doing work. The formula is Work = Power × Time. Here, Work = 500 watts × 10 seconds = 5000 joules. Therefore, the correct answer is 500 J.