Physics - 10 Force and Motion - 10.1 Force and Acceleration & 10.2 Weight and Terminal Velocity & 10.3 Forces and Braking

force =

mass x acceleration

F =

ma

Newton's second law of motion [2]

- acceleration is proportional to resultant force on object
- acceleration is inversely proportional to mass of object

Proportionality statement for F = ma

F ∝ ma

Inertia

tendency of an object to resist a change in its motion

Inertial mass

measure of an object's resistance to any type of force

Inertial mass =

force ÷ acceleration

Weight

measure of the force of gravity on an object

Mass

measure of the amount of matter in an object

Weight vs. mass [2]

- mass is quantity of matter
- weight is force of gravity upon that matter

Unit of weight

newtons, N

Unit of mass

kilograms, kg

weight =

mass x gravitational field strength

W =

mg

Unit of gravitational field strength

newtons per kilogram, N/kg

Terminal velocity

greatest velocity a falling object can reach

When does an object reach terminal velocity? [4]

- frictional force is equal and opposite to weight
- so resultant force is zero
- so acceleration is zero
- so the velocity remains constant

Stopping distance

shortest distance a vehicle can safely stop in

Stopping distance =

thinking distance + braking distance

Thinking distance

distance travelled by the vehicle in the time it takes the driver to react

Braking distance

distance travelled by the vehicle after applying the brakes

Factors affecting stopping distances [4]

- awareness of driver
- vehicle speed
- adverse road conditions
- poor vehicle maintenance