Energy, Work & Power (P1.6.1)

Abigail is conducting an experiment to measure the energy used by a small electric motor. What is energy measured in?

• Watts

• Newtons

• Kilograms

• Joules

Answer explanation

Energy is measured in Joules, which is the standard unit in the International System of Units (SI). Watts measure power, while Newtons measure force, and kilograms measure mass.

In a physics class, James and Daniel are discussing what constitutes a system. James believes that a system can be defined as a single object, while Daniel argues that it should be considered a group of objects. What do you think a system in physics is?

• A single object

• A group of objects

• A force applied

• A type of energy

Answer explanation

In physics, a system refers to a group of objects that interact with each other. This distinguishes it from a single object, a force, or a type of energy, making 'a group of objects' the correct choice.

Hannah is studying different forms of energy in her science class. Which of the following is NOT an energy store?

• Magnetic field strength

• Kinetic

• Gravitational potential

• Thermal

Answer explanation

Magnetic field strength is a measure of the intensity of a magnetic field, not an energy store. In contrast, kinetic, gravitational potential, and thermal are all forms of energy storage.

Aiden drops a ball from the top of a tall building. What happens to energy in the falling object?

• It is transferred to thermal store

• It is transferred to kinetic store

• It is lost

• It remains constant

Answer explanation

As an object falls, its gravitational potential energy is converted into kinetic energy, increasing its speed. Thus, the correct answer is that energy is transferred to the kinetic store.

Olivia is riding her bicycle down a hill. What is the formula for calculating her kinetic energy as she speeds up?

• KE = Fd

• KE = 1/2 mv^2

• KE = mv

• KE = mgh

Answer explanation

The correct formula for calculating kinetic energy (KE) is KE = 1/2 mv^2, where m is mass and v is velocity. This formula shows that kinetic energy is proportional to the mass and the square of the velocity.

While playing on the playground, Kai noticed that when he climbs to the top of the slide, he feels a sense of potential energy. What does gravitational potential energy depend on?

• Mass and speed

• Force and distance

• Height and mass

• Speed and distance

Answer explanation

Gravitational potential energy depends on an object's height above a reference point and its mass. The formula is PE = mgh, where PE is potential energy, m is mass, g is the acceleration due to gravity, and h is height.

Liam is trying to understand how much energy his new electric car uses. He learns that power is measured in a specific unit. What is the unit of power?

• Joules

• Watts

• Newtons

• Kilograms

Answer explanation

The unit of power is Watts, which measures the rate of energy transfer. Joules measure energy, Newtons measure force, and kilograms measure mass, making Watts the correct choice for power.

Daniel is conducting an experiment to measure the efficiency of a solar panel. What does efficiency measure in this context?

• Energy stored

• Energy wasted

• Useful energy output compared to input

• Total energy input

Answer explanation

Efficiency measures how much useful energy output is obtained compared to the energy input. The correct choice highlights this relationship, indicating that efficiency is about maximizing useful energy while minimizing waste.

Nora is pushing a box across the floor. If she applies a force of 10 N and moves the box a distance of 5 meters, what is the work done by Nora?

• W = P/t

• W = KE

• W = mgh

• W = Fd

Answer explanation

The correct equation for calculating work done is W = Fd, where W is work, F is force, and d is the distance moved in the direction of the force. This formula captures the essence of work in physics.

Noah is studying energy transfers in a renewable energy project. What is a Sankey diagram used for?

• To show energy transfers

• To calculate work done

• To measure power

• To define energy stores

Answer explanation

A Sankey diagram is specifically designed to visualize energy transfers, illustrating how energy moves between different states or processes. This makes 'To show energy transfers' the correct choice.