Gravity — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
A student that weighs 100 pounds on Earth weighs 100 pound on Mars too.
Corrected: A student who weighs 100 pounds on Earth weighs only 38 pounds on Mars.
Mars has about 38% of Earth's gravity, so a 100-pound person weighs about 38 pounds there.
2. Fix the sentence:
On the Moon, a 100-pound child weigh almost the same as on Earth.
Corrected: On the Moon, a 100-pound child weighs only about 17 pounds.
Moon gravity is about 1/6 of Earth's, so 100 pounds becomes about 17 pounds on the Moon.
3. Fix the sentence:
Mass and weight is the same thing on every planet you visit.
Corrected: Mass stays the same everywhere, but weight changes with each planet's gravity.
Your mass does not change, but your weight depends on local gravity strength.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. A 100-pound student on Earth would weigh about 38 pounds on Mars.
100 pounds multiplied by 0.38 equals about 38 pounds on Mars.
2. On the Moon, that same 100-pound student would weigh close to 17 pounds.
100 divided by 6 is roughly 17 pounds, the Moon weight.
3. The amount of matter in your body is called your mass.
Mass is the quantity of matter and is the same on Earth, Mars, or the Moon.
4. Gravity always pulls objects toward the center of a planet, an action called attraction.
Gravity is an attractive force that pulls masses toward each other.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Why does an astronaut weigh less on the Moon than on Earth?
Sample answer: The Moon has much less mass than Earth, so its gravity is weaker. Weaker gravity pulls on the astronaut with less force, making the astronaut weigh about one-sixth of Earth weight.
Smaller mass means weaker gravity, which means less weight for the same astronaut.
2. Explain how a 100-pound Grade 5 student would feel on Mars compared to Earth.
Sample answer: On Mars the student would weigh only about 38 pounds, so jumping and lifting things would feel much easier. Mars gravity is weaker than Earth gravity, but it still pulls the student down.
Mars gravity is about 38% of Earth's, so weight and effort needed both drop.