Gravitational Fields
How mass reaches out across space
Do Now: Astronauts on the International Space Station float. Is there no gravity up there?
There is plenty of gravity! About 400 km up, Earth’s gravitational field is still about 90% as strong as on the ground. Astronauts float because they and the station are falling around Earth together.
Try It First
Drag the test mass around the planet. Change the planet and the mass.
Lessons
Review: Gravity • Review: Weight
NYS P-12 Science Learning Standards, Physics: HS-PS2-4 — Use mathematical representations of Newton’s Law of Gravitation and Coulomb’s Law to describe and predict the gravitational and electrostatic forces between objects. (Includes quantitative and conceptual descriptions of gravitational and electric fields.)
Field Strength on Mars
A rover team calibrates a force sensor on Mars. When a 2.0-kg test mass hangs from the sensor at rest, it reads 7.4 N.
What is the gravitational field strength at the surface of Mars?
▶ Want a challenge? Open 6 more Regents-style questions (harder · mixed formats)
Challenge score: 0 / 6
C1. A team member makes the following claim.
Place a check mark in either the Support or Refute box. Justify your response using a mathematical relationship.
C2. In a field diagram of Mars, how should the gravitational field arrows be drawn?
C3. The Perseverance rover has a mass of about 1025 kg. Substitute numerical values into a mathematical representation that can be used to determine the gravitational force on the rover on Mars. Then calculate the force.
C4. An astronaut on Mars drops a rock from rest at a height of 2.0 m. Neglecting air resistance, determine how long the rock takes to reach the ground.
C5. The team replaces the 2.0-kg test mass with a 5.0-kg mass. What happens?
C6. A bathroom-style spring scale calibrated on Earth displays “kilograms.” Explain why it would show the wrong mass for the 2.0-kg test mass on Mars, and describe how the team could correct the reading.