Resultant Force
- the overall force acting on an object
- (sum of all forces combined)
Newton's Second Law
- F = m x a
- W = m x g
Newton's First Law
- if there is a resultant force, an object will accelerate or decelerate
- if there is no resultant force, an object will
- remain stationary, or
- continue at a constant speed
(if you know the names of the force, replace them e.g. weight/ air resistance/ friction/ driving force/ drag)
Skydiver reaching terminal velocity
- first, their downward force is bigger than their upward force.
- this causes them to accelerate downwards.
- then, the upward force increases (they are hitting the wind faster)
- eventually, downward force = upward force.
- this causes them to fall at a constant speed.
Car reaching terminal velocity
- first, forward force is bigger than the backwards force.
- this causes the car to accelerate forwards.
- then, the backwards force increases
- eventually, forward force = backwards force
- this causes the car to continue at a constant speed.
Newton's Third Law
- when two stationary objects interact,
- they exert an equal and opposite force on each other.
- my laptop has a weight (downward force)
- this means the table must have a reaction force (upward force)
Springs
- F = ke
- Force (N)
- extension (m)
- spring constant (N/m)
- Hooke's Law - the extension of a spring is directly proportional to the force applied - until the limit of proportionality
- Elastic - will return to original shape
- Plastic - will not return to original shape
- Elastic potential energy - energy transferred to a stretched object