Science - 7 - Energy worksheet worksheet - Free Printable

Let's solve each question step by step and explain the reasoning.

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Question 1: What is the SI unit of energy?

Options:
A. Joule
B. Newton
C. Ohm
D. Watt

Answer: A. Joule

✔ Explanation:
The SI unit of energy is the joule (J).
- Newton (N) is the unit of force.
- Ohm (Ω) is the unit of electrical resistance.
- Watt (W) is the unit of power (energy per second).

So, the correct answer is A. Joule.

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Question 2: Food is needed to supply our bodies with energy. What type of energy is present in food?

Options:
A. Light energy
B. Heat energy
C. Electrical energy
D. Chemical potential energy

Answer: D. Chemical potential energy

✔ Explanation:
Food stores energy in the form of chemical bonds. When our bodies digest food, these chemical bonds are broken down through metabolic processes (like cellular respiration), releasing chemical potential energy that powers bodily functions.
This is why food is said to contain chemical potential energy.

So, the correct answer is D. Chemical potential energy.

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Question 3: Energy changes in a hydroelectricity power station

We are given a diagram showing a hydroelectric power station with points labeled L, M, N, and O:

- L: Energy of water at the top of the dam (before it flows down)
- M: Energy of water as it flows down the pipe
- N: Energy of the turbine
- O: Energy out of the generator

We need to identify the energy types at each point.

Let’s analyze:

#### L – Water at the top of the dam
- The water is at a height → has gravitational potential energy.
- It hasn't started moving yet → no kinetic energy.
➡️ So, Gravitational Potential Energy

#### M – Water flowing down the pipe
- As the water falls, gravitational potential energy decreases, but it gains speed → kinetic energy increases.
- At this stage, it still has some height → so still has some gravitational potential energy.
- So, it has both kinetic and gravitational potential energy.
➡️ Kinetic + Gravitational Potential Energy

#### N – Energy of the turbine
- The moving water hits the turbine blades → transfers its kinetic energy to the turbine.
- This causes the turbine to spin → mechanical (kinetic) energy.
➡️ Kinetic Energy

#### O – Energy out of the generator
- The spinning turbine turns the generator → produces electrical energy.
- The output from the generator is electricity sent through power cables.
➡️ Electrical Energy

Now let’s match this with the options:

| Option | L | M | N | O |
|-------|---|----|----|----|
| A | Gravitational Potential | Gravitational Potential | Kinetic | Electrical |
| B | Gravitational Potential | Kinetic + Gravitational Potential | Kinetic | Electrical |
| C | Kinetic | Gravitational Potential | Electrical | Kinetic |
| D | Kinetic | Kinetic + Gravitational Potential | Boiling | Kinetic |

✔ Correct matches:
- L: Gravitational Potential ✔
- M: Kinetic + Gravitational Potential ✔
- N: Kinetic ✔
- O: Electrical ✔

Only Option B matches all four correctly.

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✔ Final Answers:

1. A. Joule
2. D. Chemical potential energy
3. B. Gravitational Potential, Kinetic + Gravitational Potential, Kinetic, Electrical

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✔ Boxed Answer:

1. A
2. D
3. B