Week 11 · Axis 2, Unit 2 Motion, Concept 2.1 Motion and Stopping (B) and Concept 2.2 Energy and Motion (A) · 3 lessons
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Force, work and the roller-coaster question
Discovery Education Science P4: Term 1, Unit 2, pp. 130–144
GoalExplain how force, energy and work are linked, and start asking how a roller coaster gets its energy.
New words
energy · what is needed to make things move or changework · energy used when a force moves somethingtransfer · to pass energy from one thing to another
Explanation
To start a car moving or to stop it, a push or a pull is needed. Force and energy are not the same thing, but they are linked. Imagine pushing a stalled car along a flat road. You push hard, you start to sweat, and you feel tired. Your body used energy from the food you ate. Energy moves from your body to the car, and the car starts to move. Work is the energy used when a force moves something. The harder the push and the farther the car moves, the more work is done. Now think of a roller coaster. Where does its energy come from, and what happens to it as the train moves? We will keep that question and answer it in the next lessons.
food gives the body energy→the body pushes the car→energy moves to the car and it moves
Worked examples
Youssef’s dad and his uncle push a stalled microbus to the side of the road. They use energy from their food. The energy passes to the microbus, which starts to move. Pushing it a long way is more work than pushing it a short way.
Hana kicks a ball. The force of her foot sends the ball forward. Energy moves from her leg to the ball. After the kick, the ball keeps moving until friction stops it.
At the funfair, the first part of a roller coaster is pulled up a tall slope by motors. After the top, the train races down with no motor pushing it. We ask: where does the energy for the fast ride come from?
Class activity
Three questions. A grown-up gives you a small backpack and three books. Pull the backpack along the floor empty, then with three books inside. Which was harder? Where did the energy come from? Then write three questions about roller coasters and energy, for example: Why is the first hill the tallest? Share them with a friend.
Practice
1
Where does the energy come from when you push a stalled car?
From your body; it comes from the food you eat.
2
Two children each push a box 2 m. Mariam's box is heavy and Nour's box is empty. Who does more work?
Mariam. It takes a bigger force to push the heavy box the same distance.
3
Put the steps in order. Say the letters. A: the car moves. B: food gives the body energy. C: the body pushes the car.
