Newton's law of universal gravitation

Answer Key - Grade 11 Science Worksheet

Circle the best answer, or write your answer on the line.

1. 1.

   Earth's mass is 5.9722 × 10²⁴ kg and its radius is 6371 km. With G = 6.674 × 10⁻¹¹ N·m²/kg², what is g at its surface, to the nearest hundredth, Ari?

   9.82 N/kg
2. 2.

   Mars has a mass of 6.4169 × 10²³ kg and a radius of 3389.5 km. With G = 6.674 × 10⁻¹¹ N·m²/kg², what is g at its surface, to the nearest hundredth, Bo?

   3.73 N/kg
3. 3.

   The Moon's mass is 7.346 × 10²² kg and its radius is 1737.4 km. With G = 6.674 × 10⁻¹¹ N·m²/kg², what is g at its surface, to the nearest hundredth, Esme?

   1.62 N/kg

4. Read this first

   Pull of a planet on a 100 kg probe (example data)

   Distance from center (planet radii)	Pull (N)
   1	900
   2	225
   3	100
   4	?

5. 4.

   Using the table, what pull should the probe feel at 4 planet radii, Jun?

   • 225 N
   • 75 N
   • 56.25 N
6. 5.

   Using the table, how does the pull change from 1 to 3 planet radii, Kira?

   • It drops to one-third
   • It drops to one-ninth
   • It drops by 3 N
7. 6.

   Using the table, what is the planet's g at its surface, Luz?

   • 90 N/kg
   • 900 N/kg
   • 9 N/kg
8. 7.

   A model satellite's path is 400 km above Earth's surface, and Earth's radius is 6371 km. What distance r goes into the gravity formula, Milo?

   • 400 km, the height
   • 6771 km
   • 5971 km
9. 8.

   Why is r measured between the centers of the two bodies, Pia?

   • Gravity starts at the surface
   • Surfaces are too hard to measure
   • A round body pulls as if its mass were at its center
10. 9.

    NASA gives Mars a surface gravity of 3.73 m/s². What does a 2 kg box weigh there, Ren?

    • 7.46 N
    • 2 N, the same as its mass
    • 0.54 N
11. 10.

    The Moon's surface gravity is 1.62 m/s² and Earth's is 9.82 m/s². About what fraction of its Earth weight does a box have on the Moon, Tala?

    • The same
    • About half
    • About one-sixth