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 cart resting at the top of a ramp has kinetic energy because it is up high.
Corrected: A cart resting at the top of a ramp has potential energy because it is up high.
In Grade 4 science, an object that is not moving has potential energy, not kinetic. Kinetic energy only exists when something is actually moving.
2. Fix the sentence:
A ball flying through the air has potential energy from its motion.
Corrected: A ball flying through the air has kinetic energy from its motion.
Grade 4 students learn that any object moving through space, like a ball flying, carries kinetic energy. Potential is for stored energy.
3. Fix the sentence:
A book held high above the floor has no energy until you let it go.
Corrected: A book held high above the floor has potential energy even before you let it go.
Grade 4 lessons teach that lifted objects store potential energy because of gravity. The energy is there waiting, not zero.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. A cart rolling down a hill has kinetic energy because it is moving.
Grade 4 science defines kinetic energy as the energy of motion. A rolling cart is clearly moving, so its energy is kinetic.
2. A ball sitting on a high shelf has gravitational potential energy.
In Grade 4, gravitational potential energy is stored when an object is raised. The higher the shelf, the more potential energy the ball has.
3. When you stretch a rubber band, it stores potential energy in its shape.
Grade 4 science includes elastic potential energy. A stretched rubber band stores energy that can be released when let go.
4. A swing moving back and forth shows kinetic energy as it travels.
Grade 4 students learn that a moving swing has kinetic energy. At the top of each swing it briefly has potential, but during motion it is kinetic.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Explain the difference between kinetic and potential energy using a roller coaster as an example.
Sample answer: A roller coaster has potential energy when it is at the top of a hill because the height stores energy. As it rolls down, that potential energy changes into kinetic energy of motion. The faster it moves, the more kinetic energy it has.
Grade 4 science uses roller coasters to teach energy transformation. Height gives potential, motion gives kinetic, and one changes into the other.
2. Why does a basketball held above your head have potential energy even when it is not moving?
Sample answer: The basketball has potential energy because it is raised up high. Gravity is pulling on it, so the height stores energy. If you let go, that stored energy will turn into kinetic energy as the ball falls down.
Grade 4 students learn that gravitational potential energy depends on height. A still object above the ground stores energy because of gravity.