Transport: Forces at Work

• the shape
• speed
• direction

newtons (N)

a Newton Balance

the force on it due to the Earth's gravitational pull

the amount of matter that makes up the object

the weight per unit mass of an object

a force that opposes the motion of an object

• applying the brakes of a car
• opening a parachute
• wearing rubber soled shoes for rock climbing

• making racing cars streamlined
• oiling moving parts in a car engine
• using an air cushion on an air hockey table

when equal forces act in opposite directions

• When a car brakes there is a force acting against the car slowing it down.
• If the passenger was not wearing a seatbelt they would continue to move forwards at constant speed.
• A seatbelt is therefore used to provide a backwards force to stop the
• passenger from continuing to move forward at constant speed

when balanced forces act on an object it remains at rest or continues to move at a steady speed

• When unbalanced forces act on a object the object changes speed.
• The acceleration due to an unbalanced force depends on the mass of the object.
• When the force stays constant and the mass increases, the acceleration decreases
• When the mass stays constant and the force increases, the acceleration increases