Slides in this set
What is this unit about?
Humans have always been interested in how things move
and why they move the way the do. Motion is such an
obvious part of our lives and we have been driven to try and
find laws and rules to figure out the basic principles of the
motions made by and
affecting us, and we cannot
claim to know so much about
the world if we do not understand
the basic principles of motion.
This unit is all about forces and
the way they effect movement.
How does a car start moving?
Firstly, the engine has to make the wheels turn which
causes a forward force on the car. The wheel is causing a
backwards force on the ground surface. (This is what
causes mud/dirt/sand/etc, to fly backwards). However,
the force of the cars engine is greater than it's
interaction pair's so the car starts to move in the
direction of the greater force.
What causes friction?
Friction is simply the force of two or more objects being
rubbed together which then causes things to slow
down. So the cause of it is simply two objects being
What is a reaction force and why does it
Newton's third law states that forces act in pairs. So
when a force is considered an action force, the
corresponding force is the reaction force.