Energy: Forms and Transfer — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
A slow truck has more kinetic energy than a fast bicycle of the same weight.
Corrected: A fast bicycle has more kinetic energy than a slow truck of the same weight.
Grade 4 science teaches that speed strongly affects kinetic energy. When weight is equal, the faster object always has more kinetic energy.
2. Fix the sentence:
A small marble moving fast has more kinetic energy than a heavy bowling ball moving the same speed.
Corrected: A heavy bowling ball moving fast has more kinetic energy than a small marble moving the same speed.
In Grade 4, students learn that mass also affects kinetic energy. At the same speed, a heavier object carries more kinetic energy than a lighter one.
3. Fix the sentence:
Two cars moving at the same speed always have exactly the same kinetic energy no matter their size.
Corrected: Two cars moving at the same speed have different kinetic energy if their sizes are different.
Grade 4 science says kinetic energy depends on both mass and speed. A bigger car at the same speed will carry more kinetic energy than a smaller one.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. When a car speeds up, its kinetic energy increases.
Grade 4 students learn that increasing speed always increases kinetic energy. The faster something moves, the more energy it carries.
2. A heavy bowling ball has more kinetic energy than a light tennis ball when both move at the same speed.
Grade 4 science compares objects of the same speed to show that mass matters. The heavier object has more kinetic energy when speed is equal.
3. Doubling the speed of a moving object makes its kinetic energy greater than before.
In Grade 4, students learn that doubling speed greatly increases kinetic energy. Even small speed changes lead to big energy changes.
4. A still object that is not moving has zero kinetic energy.
Grade 4 lessons teach that kinetic energy requires motion. An object at rest has zero kinetic energy, though it may still have potential.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Why does a fast soccer ball hurt more when it hits you than a slow one of the same size?
Sample answer: The fast soccer ball has more kinetic energy because speed makes kinetic energy bigger. When it hits you, more energy transfers to your body. The slow ball carries less energy, so it does not push as hard.
Grade 4 science explains that kinetic energy increases with speed. A faster object hits with more force because more energy moves into the thing it strikes.
2. Compare a moving truck and a moving bicycle traveling at the same speed. Which has more kinetic energy and why?
Sample answer: The truck has more kinetic energy because it has much more mass than the bicycle. When two objects move at the same speed, the heavier one carries more kinetic energy. That is why a truck is harder to stop than a bike.
Grade 4 students learn that kinetic energy depends on both mass and speed. With equal speed, the heavier object has more kinetic energy and is harder to stop.