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?

   • Nothing; it just keeps the ball tidy and in one place
   • A push from behind the planet
   • The planet's forward motion
   • The Sun's gravity pulling the planet inward
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 stops circling and hangs still
   • It goes around faster, like a closer planet
   • It flies off in a straight line
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 speeding up in its orbit
   • The planet falling into the Sun
   • The Sun pushing the planet away
4. 4.

   “Orbit diagram from above, not to scale:” Luz's friend says planets keep orbiting because nothing in space can stop them, so gravity is not needed. Which response is best?

   • Disagree: they need rocket engines to keep them going around
   • Agree: wind in space steers them
   • Agree: motion alone keeps them circling
   • Disagree: without gravity they would move in straight lines
5. 5.

   A post says the Sun orbits Earth once a day. Milo checks it. Which response is best?

   • Disagree: Earth spins daily and orbits the Sun yearly
   • Agree: we see the Sun cross the sky
   • Agree: Earth is the center of the solar system
   • Disagree: the Sun orbits Earth once a year, not once a day

6. 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.

7. 6.

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

   • Exactly 365 days
   • Between 365 and 687 days
   • Less than 365 days, since it is farther out
   • More than 687 days
8. 7.

   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?

   • Faster than 47.4 km/s
   • Zero, since it is so near the Sun
   • Exactly 29.8 km/s, like Earth
   • Slower than 47.4 km/s, since it is closer
9. 8.

   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?

   • Much less time than 27.3 days
   • Exactly 27.3 days, like the Moon
   • Forever, since it is too close to move
   • More than 27.3 days, since it is closer
10. 9.

    “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?

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

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