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?

   • 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
   • 4.9 m/s², from mg sin 30° alone

5. Read this first

   Free-body diagram (example data)

   a block sliding down a 30° ramp of mass 4 kg, with arrows from its center: weight 39.2 N straight down; normal force 33.9 N out of the ramp; sliding friction 6.8 N up the ramp.

6. 5.

   Using the diagram, about what is the block's acceleration down the ramp, Luz?

   • About 3.2 m/s² down the ramp
   • About 6.6 m/s² down the ramp, adding friction
   • About 4.9 m/s² down the ramp, ignoring friction
   • About 1.7 m/s² down the ramp, from 6.8 ÷ 4
7. 6.

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

   • Disagree: the normal force is larger than the weight on a ramp
   • Agree: the ramp's tilt changes the weight but not the normal force
   • Disagree: it balances only the weight's part into the ramp
   • Agree: the surface always pushes back with the full weight
8. 7.

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

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

9. 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. 8.

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

    • Static friction from the truck bed, pointing forward
    • The normal force from the bed, pointing forward
    • The box's inertia pushing it along with the truck
    • The force of the truck's motion carried over to the box
11. 9.

    The static friction coefficient between box and bed is 0.4. At what acceleration does the 10 kg box begin to slip, Tala?

    • About 39 m/s², the maximum friction force itself
    • About 3.9 m/s², whatever the box's mass
    • About 0.4 m/s², the friction coefficient itself
    • About 9.8 m/s², the acceleration of free fall
12. 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 speeding up, middle at steady speed, smallest slowing
    • Largest at steady speed, since the load moves fastest then
    • Largest when slowing down, since the drone works hardest to stop
    • The same in the three stages, since the load moves upward the whole time