Why things keep moving or stay still (balanced and unbalanced forces)
Grade 8 Science Worksheet - Building Confidence
Circle the best answer, or write your answer on the line.
Ari pushes a box of books across the floor. The forces point opposite ways, so subtract them. What is the net force?
Read this first
Use this
Force arrow diagram, one dimension, arrows drawn to scale by size.
Bo pushes a moving box across the floor. The forces point opposite ways, so subtract them. What is the net force?
Esme pushes a laundry basket across the floor. The forces point opposite ways, so subtract them. What is the net force?
Jun slides a box across the classroom floor. Are the forces balanced, and what happens to the box?
- Balanced; it keeps the same speed
- Unbalanced; it slows down
- Unbalanced; it speeds up
- Balanced; it must stop
Use this
Force arrow diagram, one dimension, arrows drawn to scale by size. Box A: pull 12 N pointing right; friction 12 N pointing left. Beside it: rolling right at a steady speed.
Kira pulls a wagon along the sidewalk. Read the arrows. What happens to the wagon's motion?
- It slows, since the pull is used up
- It speeds up to the right
- It keeps rolling at the same speed
- It stops, since the forces are balanced
Luz pushes a chair with wheels that is sitting still. Are the forces balanced, and what happens?
- Unbalanced; it starts moving right
- Unbalanced; it moves left
- Balanced; it moves at a steady speed
- Balanced; it stays still
Pia reads that a bowling ball has a lot of inertia. What does that mean?
- It feels no friction
- A force inside it keeps pushing it
- It rolls very fast
- It is hard to start or stop
Ren bikes at a steady 5 m/s. The forces on the bike balance. What happens next?
- It slows down, since it needs more push
- It keeps going 5 m/s
- It speeds up a little
- It stops soon, since forces balance
Use this
Force arrow diagram, one dimension, arrows drawn to scale by size. Box A: push from the wind 3 N pointing right; water drag 3 N pointing left. Beside it: moving right at a steady 2 m/s.
Tala's toy sailboat crosses a pond at a steady 2 m/s with balanced forces. What happens to its motion?
- It stays the same, 2 m/s
- It slows, since it is not pushed harder
- It stops, since balanced means still
- It speeds up to the right
A dictionary sits on Zee's desk. Gravity and the desk's support balance. What happens to the book?
- It starts to slide
- It sinks into the desk
- It needs a push to stay put
- It stays at rest