Forces and motion

• Force is measured in Newtons.
• The weight of an object is the pull of gravity on it.
• When two objects touch, there is a contact force.
• Friction opposes motion.
• Air resistance or drag is the force of friction when an object moves through air or water.
• Upthrust is the upward push of a liquid or gas on an object. (This makes you able to float in pools)
• Force can be represented in arrows.
• A force can make an object change speed.
• A force can change the direction in which an object is moving.
• Subtract one force from another to get resultant force.
• If there is no resultant force, then the object is balanced.
• No resultant force means that an object is no longer accelerating and is continuing at a constant speed in a straight line.
• The force of gravity acting on an object is it's weight.
• Earth pulls with a force of approximately 10 N.
• An object of 1kg has a force of 10 N.
• Gravitational force per unit mass --> g = 10N/kg
• Weight = mass x gravitational force per unit mass --> W=mg
• Force = Mass x Acceleration