Draw free-body diagrams and find the net force

Answer Key - Grade 11 Science Worksheet - Challenge Me

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

1. 1.

   Ari pulls a 10 kg wagon with 50 N at 37° above the ground. The sliding friction coefficient is 0.2. To 0.01 m/s², what is its acceleration?

   2.63 m/s²
2. 2.

   Bo pulls a 20 kg wagon with 100 N at 30° above the ground. The sliding friction coefficient is 0.3. To 0.01 m/s², what is its acceleration?

   2.14 m/s²
3. 3.

   Esme pulls a 8 kg wagon with 40 N at 60° above the ground. The sliding friction coefficient is 0.25. To 0.01 m/s², what is its acceleration?

   1.13 m/s²
4. 4.

   “Free-body diagram (example data):” Using the diagram, what is the block's acceleration down the ramp, Jun?

   • 4.9 m/s², from mg sin 30° alone
   • 9.8 m/s², the acceleration of free fall in the open
   • 2.45 m/s², half of g sin 30° because of the slope
   • 8.5 m/s², from g cos 30°, the part into the ramp
5. 5.

   Two free-body diagrams side by side (example data). Using the diagrams, about what is the rope's tension, Kira?

   • About 7.8 N, which is 2 kg × 3.92 m/s²
   • About 29.4 N, the weight of the block on the table
   • About 19.6 N, the weight of the hanging block
   • About 11.8 N, which is 3 kg × 3.92 m/s²
6. 6.

   Milo says the normal force on a block on a 30° ramp equals its weight. Agree or disagree?

   • Disagree: it balances only the weight's part into the ramp
   • Agree: the ramp's tilt changes the weight but not the normal force
   • Agree: the surface always pushes back with the full weight
   • Disagree: the normal force is larger than the weight on a ramp
7. 7.

   Noah says a scale in a rising elevator always reads more than the person's weight. Agree or disagree?

   • Disagree: it reads more only if the lift speeds up upward
   • Disagree: the scale reads less when the elevator is moving up
   • Agree: moving upward adds to the person's weight on the scale
   • Agree: the scale reads the elevator's speed times the mass
8. 8.

   Pia says that with no air, a heavier ball falls faster because gravity pulls it harder. Agree or disagree?

   • Disagree: lighter balls fall faster because they have less weight
   • Disagree: the extra pull is cancelled by the extra mass, so a = g
   • Agree: a bigger weight means a bigger acceleration
   • Agree: heavier balls reach the ground first, as experiments show

9. Read this first

   Free-body diagram (example data)

   a box on a truck bed that is speeding up forward of mass 10 kg, with arrows from its center: weight 98 N down; normal force 98 N up; friction from the truck bed ? N forward.

10. 9.

    A box on a truck bed speeds up with the truck and does not slip. What force accelerates it, Ren?

    • The box's inertia pushing it along with the truck
    • The force of the truck's motion carried over to the box
    • The normal force from the bed, pointing forward
    • Static friction from the truck bed, pointing forward
11. 10.

    A drone lifts a load up: speeding up, then at a steady speed, then slowing down. How does the cable's tension compare, Zee?

    • Largest at steady speed, since the load moves fastest then
    • The same in the three stages, since the load moves upward the whole time
    • Largest when slowing down, since the drone works hardest to stop
    • Largest speeding up, middle at steady speed, smallest slowing