How gravity holds the solar system together

Grade 6 Science Worksheet - Challenge Me

Circle the best answer.

1. 1.

   Outdoors, Esme's teacher swings a soft ball on a string to model a planet's orbit. In the model, what does the string stand for?

   • A push from behind the planet
   • The Sun's gravity pulling the planet inward
   • Nothing; it just keeps the ball tidy and in one place
   • The planet's forward motion
2. 2.

   the ball's circle shrinking as the string is pulled shorter. While the ball is swinging, the teacher slowly pulls the string shorter. How does the ball's trip around change, as Jun observes?

   • It goes around slower, like a farther planet
   • It flies off in a straight line
   • It stops circling and hangs still
   • It goes around faster, like a closer planet
3. 3.

   The ball leaving the circle in a straight line after the string is let go. In the string model, what does letting go of the string stand for, by Kira's reasoning?

   • Gravity switching off, so the planet moves in a straight line
   • The planet falling into the Sun
   • The planet speeding up in its orbit
   • The Sun pushing the planet away
4. 4.

   Noah's cousin says gravity matters for planets but not for whole galaxies. Which response is best?

   • Disagree: gravity holds the Milky Way's stars together
   • Agree: galaxies are too big for gravity
   • Disagree: galaxies are held together by wind between the stars
   • Agree: stars are held in place by light

5. Read this first

   Use this

   Table (NASA Planetary Fact Sheet), with columns Planet, Distance (millions of km) and Orbit time (days), distance from the Sun and orbit time: Mercury 57.9 million km, 88.0 days; Venus 108.2 million km, 224.7 days; Earth 149.6 million km, 365.2 days; Mars 228.0 million km, 687.0 days.

6. 5.

   An object orbits the Sun at 180 million km. Using the NASA table, about how long does its orbit take, by Pia's reasoning?

   • More than 687 days
   • Between 365 and 687 days
   • Less than 365 days, since it is farther out
   • Exactly 365 days
7. 6.

   Mercury 47.4 km/s; Venus 35.0 km/s; Earth 29.8 km/s. A space probe orbits the Sun even closer than Mercury. About how fast does it move, judging from the NASA table, by Ren's reasoning?

   • Zero, since it is so near the Sun
   • Faster than 47.4 km/s
   • Slower than 47.4 km/s, since it is closer
   • Exactly 29.8 km/s, like Earth
8. 7.

   Orbit diagram from above, not to scale: Earth with the Moon's orbit far out and a satellite's orbit close in. The Moon orbits Earth in about 27.3 days at about 384,000 km. A satellite orbits much closer. How long does its trip probably take, says Tala?

   • More than 27.3 days, since it is closer
   • Forever, since it is too close to move
   • Much less time than 27.3 days
   • Exactly 27.3 days, like the Moon
9. 8.

   “not to scale” Suppose the Sun had more mass but stayed the same distance away. What would happen to its pull on Earth, by Zee's reasoning?

   • The pull would be weaker
   • The pull would be stronger
   • No change, since distance decides it alone
   • The Sun would push Earth away
10. 9.

    Earth with the Moon's present orbit and a larger dashed orbit. If the Moon were much farther from Earth, how would its orbit change, as Ari predicts?

    • It would leave in a straight line at once
    • A stronger pull and a quicker trip
    • A weaker pull, slower motion and a longer trip
    • Nothing about its orbit would change
11. 10.

    Long ago, a huge cloud of gas and dust pulled together to form the Sun and the planets. Which force did that, as Bo reads from NASA?

    • Wind blowing the dust together
    • Gravity
    • Earth's gravity, from the center of everything
    • No force; it happened by itself