What is this skill?
A force is a push or a pull. Forces make things start moving, stop, speed up, slow down or change direction. Third graders learn three forces by name: gravity pulls things down toward the ground, friction slows things that rub against each other, and a magnet can pull on certain objects without touching them. They also learn that a bigger force makes a bigger change.
In this practice a child answers "A force is a ___" (push or pull), sorts actions into push (kicking a ball, pressing a doorbell, hitting a baseball) or pull (opening a drawer, tug-of-war, dragging a sled), and decides which surface has the most friction (rough carpet, not wet tile or smooth ice). Other questions ask which way a dropped ball goes (down), what happens when a harder push meets a toy car (it goes faster), how bike brakes stop a wheel (friction between the brake and the wheel) and what happens when two kids push a box equally hard from opposite sides (it stays still). A second sort asks for more friction or less friction: sandpaper, a rubber shoe sole and carpet against ice, wet soap and a polished floor. The hardest questions ask why you slide farther on ice than on grass (ice has less friction) and why a heavy box is hard to push (it needs a bigger force to get moving).
Why it matters
Forces and motion are the start of physics, and they explain nearly every game a child plays. Why does a swing slow down? Why is it hard to run in sand? Why does a ball roll farther on a smooth floor? The answers are all forces.
The skill builds scientific reasoning, because the questions ask why. A third grader who can explain that ice has less friction than grass is using evidence and comparing, not just recalling a word.
It also prepares children for later ideas such as speed, energy and engineering. A bike brake and a sled run are real machines to think with.
Common mistakes
- Thinking a ball keeps rolling forever once it is pushed. On grass, friction slows it down until it stops. Rolling farther on a smooth floor is a clue that there is less friction.
- Saying a force is only a push. A pull counts, too: opening a drawer, tugging a rope and gravity itself.
- Mixing up friction and gravity. Gravity pulls things down toward Earth. Friction works when two surfaces rub, and it slows the movement.
- Assuming that if nothing moves, no forces are acting. In the box example, two equal pushes from opposite sides cancel out, so the box stays still.
How to help at home
- Slide a toy car down a ramp made from a book and a board. Cover the board with a towel, then paper, then foil, and ask which surface let the car go farthest.
- Try a tug-of-war with a rope or scarf and talk about the pulling. Then try pushing a box together from opposite sides.
- Rub your hands together fast, then rub them with a little lotion. Ask which has more friction and what you felt.
- Drop two different objects from the same height and watch them fall. Ask what is pulling them down.
Worked examples
These are real questions from the Tutorsaurus forces and motion practice, with the answers worked out.
Example 1
A ball rolling on grass will keep rolling forever.
Answer: False. False! Friction from the grass slows the ball until it stops.
Example 2
How do bike brakes stop the wheel?
Choices: Friction between the brake and wheel, Gravity pulls harder, The wind pushes back
Answer: Friction between the brake and wheel. Brakes squeeze the wheel. The rubbing makes friction, and friction slows the wheel down.
Example 3
Why do you slide farther on ice than on grass?
Choices: Ice is heavier, Ice has less friction, Grass has more gravity
Answer: Ice has less friction. Ice is smooth, so there is less friction to slow you down. Grass is rough and stops you faster.
Printable worksheet (PDF) — one page of questions from this practice that work on paper, easier ones first, with an answer key on page 2. Free to print, no sign-up.