Balanced forces, equilibrium and inertia

Answer Key - Grade 11 Science Worksheet - Challenge Me

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

1. 1.

   Ari hauls a 20 kg crate up a 30° ramp at constant velocity with a rope parallel to the ramp. Sliding friction is 25 N. What is the rope's tension, to 0.1 N?

   123 N
2. 2.

   Esme hauls a 50 kg crate up a 37° ramp at constant velocity with a rope parallel to the ramp. Sliding friction is 60 N. What is the rope's tension, to 0.1 N?

   354.9 N

3. Read this first

   Use this

   The block is just about to slide.

5. 3.

   The block is just about to slide. Using the diagram, what is the least coefficient of static friction, Jun?

   • About 0.75
   • About 0.80
   • About 1.33
   • About 0.60
6. 4.

   A 10 kg block of the same material replaces the 5 kg block on the same ramp. Does it start to slide at a different angle, Kira?

   Use the picture in question 3.

   • Yes: friction grows with weight, so it slides at a larger angle
   • No: the normal force is the same for both blocks
   • Yes: the heavier block slides at a smaller angle than the lighter one
   • No: weight and the friction limit both double, so the angle holds
7. 5.

   “example data” Using the diagram, which cable has the greater tension, Luz?

   • The right cable, at 60°, since it carries more of the weight
   • The left cable, since 30° is the smaller angle
   • The left cable, at 30°, since a flatter cable pulls much harder
   • Neither cable: both pull 98 N, by the symmetry of the sign
8. 6.

   Milo says a skydiver falling at a steady speed has no forces acting. Agree or disagree?

   • Disagree: drag and weight both act, and they cancel
   • Disagree: gravity acts alone, so the diver speeds up
   • Agree: drag appears when the diver speeds up
   • Agree: a steady speed means that no force acts on the diver
9. 7.

   A 2,000 kg truck and 1,000 kg car go equally fast. Pia says the same braking force stops both in the same distance. Agree or disagree?

   • Agree: they start at the same speed, so both stop in the same distance
   • Disagree: the truck has twice the inertia and needs twice the distance
   • Agree: braking force depends on speed, not on mass
   • Disagree: the car needs twice the distance, since it is lighter
11. 8.

    A ball hangs from a train ceiling as the train speeds up, and the string tilts. Seen from the ground, what supplies the ball's forward acceleration, Ren?

    • Its own inertia pushing it forward as the train speeds up
    • The horizontal part of the string's tension
    • The horizontal part of its weight, pointing toward the front
    • A forward force carried over from the train's motion
12. 9.

    The string stays 30° from the vertical while the train speeds up. What is the train's acceleration, Tala?

    Use the picture in question 8.

    • About 5.7 m/s²
    • About 8.5 m/s²
    • About 17 m/s²
    • About 4.9 m/s²
13. 10.

    In a jet cruising at a steady 250 m/s, Zee drops a coin. Where does it land compared with the feet?

    • At the feet, since it keeps the jet's forward velocity
    • Behind the feet, since the air in the cabin holds it back
    • Several meters behind the feet, since the jet moves on
    • Ahead of the feet, since the jet's speed adds to the coin's fall