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Force & Motion Vocabulary

Science · Forces & Motion · ages 9-11

Name ______________________ Date ____________

A cart is rolling along a straight track. Its resultant force becomes zero. What happens to its speed while the resultant stays zero?
- It stays the same
- It keeps falling until the cart stops
- It keeps rising until a larger force acts
- It falls at first, then begins to rise
Forces on one object cancel out, giving a resultant of zero. What are these forces called?
- Balanced forces
- Unbalanced forces
- A turning moment
A lever pivots around a fixed point called the fulcrum.
Circle one: True False
What name describes the total effect of all the forces on one object, taking their directions into account?
- A turning moment
- Resultant force
- A lever's fulcrum
Two pushes act on a cart along the same line: 8 N right and 3 N right. All other forces cancel. What is the size of the resultant force in newtons?
Answer: ______________
A level lever balances a load when you push downward. Keep the load and fulcrum in place. Which change lets you balance the same load with less effort?
- Push closer to the fulcrum while leaving the load in place
- Push at the fulcrum while leaving the load in place
- Push farther from the fulcrum
- Make the load heavier while leaving your push in place
A box has a 7 N push right and a 4 N push left. All other forces cancel. What is the size of the resultant force in newtons?
Answer: ______________
Two horizontal pushes act on a box: 6 N right and 3 N left. All other forces cancel. How would you describe the two pushes?
- Equal, balanced forces
- Forces with zero resultant
- Unbalanced forces
Two friends sit on opposite sides of a resting, level seesaw. The heavier friend sits closer to the fulcrum. Ignore the bar's weight and pivot friction. What explains its balance?
- The heavier friend's weight must equal the lighter friend's weight
- Only their distances matter, so their weights cannot affect the balance
- Their moments in opposite turning directions are equal
Mia says, "Two people are pushing a box, so their pushes must be balanced." What must she check about these two pushes?
- Whether both people push on the box at exactly the same time
- Whether the pushes are equal in size and opposite in direction
- Whether both people stand at exactly the same distance from the box

Answer key

For grown-ups. Fold this page away before handing over the rest.

Force & Motion Vocabulary W1-mt_F3ATPTCYm6-s1

It stays the same · A zero resultant means balanced forces. The cart is already moving, so it keeps the same speed along the straight track.
Balanced forces · Balanced forces cancel when combined. Their resultant is zero, even though forces are still acting.
True · The fulcrum is the fixed point a lever turns around.
Resultant force · The resultant force combines all the forces with their directions. It can be zero when the forces balance.
11 · Both pushes point right, so add their sizes: 8 plus 3 = 11. The resultant is 11 N right.
Push farther from the fulcrum · A downward push farther from the fulcrum has more turning effect for the same force. Less effort can then balance the unchanged load.
3 · Opposite forces subtract: 7 minus 4 = 3. The resultant has size 3 N and points right.
Unbalanced forces · The opposite pushes have different sizes. They leave a nonzero resultant, so they are unbalanced.
Their moments in opposite turning directions are equal · A larger weight at a shorter distance can give the same moment as a smaller weight farther away. Equal opposite moments keep this resting seesaw balanced.
Whether the pushes are equal in size and opposite in direction · Two pushes do not balance just because both exist. To cancel each other, they must have equal sizes and opposite directions.