Balanced and Unbalanced Forces

What You'll Learn

Balanced forces are equal in size and opposite in direction, so an object stays still or moves at constant speed. Unbalanced forces cause an object to accelerate or change direction.

Key Words

simple machine
lever
pulley

Materials Needed

string
weights
tape

Safety First

Be careful with scissors — ask an adult for help if needed.

Steps

Step 1 — Read

Read the introduction and identify the main idea of this lesson.

Step 2 — Do

Test friction: pull a weighted box across 4 surfaces (carpet, tile, sandpaper, foil). Use a spring scale to measure the force needed for each.

Step 3 — Observe

Look for patterns in your observations.

Step 4 — Record

Make a graph or chart showing your results.

Check Your Understanding

Question 1

1 of 3

What do balanced forces result in?