Forces & Motion
Apply Newton's Laws to real-world situations and solve problems involving force, mass, and acceleration.
Forces & Motion
Apply Newton's Laws to real-world situations and solve problems involving force, mass, and acceleration.
Science - Grade 6-8
- 1
State Newton's First Law of Motion in your own words.
An object at rest stays at rest, and an object in motion stays in motion at the same speed and direction, unless acted on by an unbalanced force (inertia). - 2
A 5 kg box is pushed with a net force of 20 N. What is its acceleration?
a = F/m = 20/5 = 4 m/s^2 - 3
What force is needed to accelerate a 1200 kg car at 3 m/s^2?
F = ma = 1200 x 3 = 3600 N - 4
A ball rolls across the floor and eventually stops. What force caused it to stop?
Friction. The friction between the ball and the floor acts opposite to the direction of motion, slowing the ball. - 5
Two teams in a tug-of-war pull the rope with equal force. What is the net force? What happens to the rope?
Net force = 0 N; the forces are balanced and the rope does not move. - 6
State Newton's Third Law and give an everyday example.
For every action there is an equal and opposite reaction. Example: pushing off a wall, rocket thrust, or jumping off a boat. - 7
A 60 kg person stands on Earth (g = 10 m/s^2). What is their weight?
W = mg = 60 x 10 = 600 N - 8
A net force of 8 N acts on a 4 kg object, giving an acceleration of 2 m/s^2. If the mass is doubled to 8 kg with the same force, what happens to the acceleration?
New acceleration = F/m = 8/8 = 1 m/s^2; the acceleration is halved.