Force and Motion

Displacement

The distance and direction an object moves in a straight line from start to end point

Speed

v = s (distance) / time

Walking speed

1.5 m/s

Running speed

3 m/s

Sound

330 m/s

Velocity

v = s/t + direction

Circles and velocity

If an object moves at a constant speed in a circle then its velocity is constantly changing

D/t graph - curves

Object is constantly increasing in speed (accelerating)

Draw tangent at specific point and find gradient

Acceleration

a (m/s²) = change in velocity (m/s) / time

Gradient in V/t graph

Acceleration of an object

Horizontal = constant velocity

Under line = displacement

Constant Acceleration

v² (final) - u² (initial) = 2as

Objects falling towards Earth

Initially accelerates at around 9.8m/s² due to force of gravity

Terminal Velocity

Air resistance balances due to gravity - here the object stops accelerating and moves at a constant velocity

Newtons 1st Law

If resultant force acting on an object is 0, it remains stationary.

If resultant force acting on a moving object is 0, it will continue moving with the same velocity

Newtons 2nd Law

The acceleration of an object is proportional to the resultant force acting on the object

And is inversely proportional to mass of object

Force needed to accelerate an object

F = m x a

Inertia

An object will remain stationary or continue moving at the same speed and direction unless a resultant force is applied

Inertial mass

how difficult it is to change the velocity of an object

inertial mass is defined as the ratio of force over acceleration

Newtons 3rd Law

Whenever two objects interact the forces they exert on each other are equal and opposite

Stopping time

Total distance travelled from when the driver first spots the obstruction to when the car stops

Thinking distance

Distance travelled by car during driver’s reaction time

Reaction time

Time taken for driver to spot obstruction and make a decision and then move their foot to the brake

Braking distance

The distance the car travels when the driver applies the brakes to when the car stops

Momentum

p (momentum kg m/s) = m x v

Conservation of momentum

Total momentum before event is equal to total momentum after in a closed system

Change in momentum

F = m/ change in velocity/ change in time