Newton's Laws of Motion
This law states that an object in motion stays in motion unless acted upon by an unbalanced force.
Newton’s 1st Law
In a free-body diagram, arrows represent these.
Forces acting on the object
The formula for acceleration is ___?
a = (vₓ – vᵢ) / t
What type of force causes an object to slow down or stop moving?
Friction
Two people push a box in the same direction (10 N + 15 N). What is the net force?
25 N in that direction
Which law explains why pushing a heavier box requires more force to move it than a lighter one?
Newton’s 2nd Law
What does the length of the arrow in a free-body diagram represent?
The magnitude (strength) of the force
A car speeds up from 5 m/s to 25 m/s in 5 s. What’s the acceleration?
(25–5)/5 = 4 m/s²
What two factors affect gravitational force between two objects?
Mass and distance
One person pushes right with 20 N and another pushes left with 15 N. What’s the net force and direction?
5 N right
When a rocket launches, the gases push down while the rocket moves up. Which law is demonstrated?
Newton’s 3rd Law
Draw or describe a free-body diagram for a book resting on a table.
Gravity down, normal force up (balanced)
A 10 N force acts on a 2 kg object. What’s its acceleration?
a = F/m = 10/2 = 5 m/s²
Why do objects fall at the same rate on the Moon?
Because there is lower gravity and no air resistance.
A toy car moves at a constant speed. What is the net force?
0 N (balanced)
A car suddenly stops and you lurch forward. Explain using Newton’s laws.
Your body’s inertia keeps it moving forward (1st Law)
A skydiver falls at a constant speed. What does this say about the forces?
Air resistance = gravity (balanced)
A 6 kg cart accelerates at 3 m/s². What’s the net force?
F = ma = 18 N
How does friction affect motion?
It opposes motion and causes slowing/stopping
A parachutist’s velocity decreases. What can you say about air resistance compared to gravity?
Air resistance > gravity (net force upward)
Compare and contrast how Newton’s 1st and 3rd laws apply to a skateboarder kicking off the ground.
1st Law: Keeps moving; 3rd Law: Push vs reaction push
A car accelerates forward. Which forces are unbalanced, and in which direction?
Forward driving force > backward friction
If a runner doubles their mass but applies the same net force, what happens to their acceleration?
It’s cut in half (inverse relationship)
Explain why a hockey puck glides longer on ice than on carpet.
Less friction on ice → less opposing force
A soccer ball is kicked into the air and comes back down. Describe how the net force changes throughout its path.
Upward kick > gravity, then gravity > motion as it slows and falls