Draw free-body diagrams and find the net force

Answer Key - Grade 11 Science Worksheet - Building Confidence

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

1. 1.

   A 2 kg cart is pushed 12 N to the right while friction pulls 3 N to the left. What is its acceleration, Ari?

   4.5 m/s²
2. 2.

   A 4 kg cart is pushed 30 N to the right while friction pulls 18 N to the left. What is its acceleration, Bo?

   3 m/s²
3. 3.

   Using the free-body diagram, what is the box's acceleration, Jun?

   • 2.5 m/s² to the right
   • 5.5 m/s² to the right, from (8 + 3) ÷ 2
   • 4 m/s² to the right, from the 8 N pull alone
   • 0 m/s², since the up and down forces cancel each other
4. 4.

   Using the diagram, how does the 5 kg crate move, Kira?

   • It speeds up downward at 8 m/s², from 40 ÷ 5
   • It moves at a steady speed, since the rope holds it up
   • It speeds up downward at 1.8 m/s²
   • It speeds up upward at 1.8 m/s², since the rope pulls up
5. 5.

   Using the diagram, about what is the skydiver's acceleration, Luz?

   • About 15.5 m/s² downward, from (686 + 400) ÷ 70
   • About 4.1 m/s² downward
   • About 9.8 m/s² downward, the acceleration from gravity alone
   • About 5.7 m/s² downward, from the 400 N of drag alone
6. 6.

   A rope pulls a wagon forward. Which force does not belong on the wagon's diagram, Noah?

   • The rope's pull on the wagon
   • The normal force from the ground on the wagon
   • Friction from the ground on the wagon's wheels
   • The wagon's pull on the rope
7. 7.

   A book rests on a desk. Which force does not belong on the book's diagram, Pia?

   • The book's push down on the desk
   • Static friction if the desk is tilted slightly
   • Earth's pull on the book, which is its weight
   • The desk's normal force up on the book
8. 8.

   A ball launched straight up by a spring toy is still rising. With no air, which forces act on it, Ren?

   • No force while it rises, then gravity at the top
   • Gravity down and the launch force up
   • Gravity down and a force of its motion up
   • Only gravity, downward
9. 9.

   A book slides across a desk after being released by the hand. Which forces are on it now, Tala?

   • Weight, normal force and friction backward
   • Weight and normal force, since it keeps moving by itself
   • Weight, normal force and a force of motion forward
   • Weight, normal force, friction backward and the hand's push forward
10. 10.

    A cart rolls at a steady speed on a smooth, level track. Which forces act on it, Zee?

    • Weight and normal force, which cancel
    • Weight, normal force and a forward force equal to its speed
    • No forces act, since a moving cart is on its own
    • Weight, normal force and a forward force that keeps it moving