Physics pt3

Scalar quantity

only has a size (magnitude)

Vector quantity

has both a size and direction

Force

a push or pull that acts on an object due to the interaction with another object

Contact force

when objects are physically touching (e.g., friction, air-resistance, tension, normal contact force)

Non-contact force

when objects are physically separated (e.g., gravitational, electrostatic, magnetic)

Interaction between forces

the forces are the same size

Opposite forces interaction

forces are in opposite directions

Resultant force on an object

zero

Centre of mass

the point through which the weight of an object can be considered to act

Turning effect of a force

a moment

Clockwise and anticlockwise moments on a balanced object

sum of all the clockwise moments about any point = sum of all the anticlockwise moments about that point

Lever reducing force

by increasing the distance from the pivot

Moment of a force with small gear driving a large gear

moment is increased

Newton's First Law

the velocity of an object will only change if a resultant force is acting on it

Resultant force on a stationary object

zero

Newton's Third Law

when two objects interact they exert equal and opposite forces on each other