What is Force?

1) Force is a push or pull 2) Force is the capacity to do work or cause

physical change 3) Force= Mass times acceleration (F = ma) 4) A force is that which changes or tends to

change the state of rest or motion of a body.

GROUPS OF FORCES: A. Contact Forces : 1. frictional force (friction)- caused by the rubbing of two objects.

2. buoyant force (buoyancy)- it is the upward force of fluids on floating objects.

3. normal force- is the support force on an object which is in contact with another stable object.

4. air resistance force - type of frictional force upon objects as they travel through the air.

5. Tension force - is the pulling force through a string, rope, cable or wire.

6. Spring force - is the force exerted by a compressed or stretched spring upon any

object which is attached to it.7. Applied force - is a force which

is made to an object by a person or another object.

B. Action-at-a-distance forces :

1. gravitation- is the force with which the earth, moon, or other very large object attracts another object towards itself.

2. Electrostatic force – is the force between particles that are caused by their electric charges.

Electric force -

3.magnetic forces – is the force made between magnetic poles

Common Units of Force --->>SI: Newton (N) 1 N = 0.225 lb; One Newton (N) of force is defined as the

amount of force needed to accelerate 1 kilogram (kg) of mass at a rate of 1 meter per second squared (m/s2).

1 Newton = 1 kg m/sec2 (A kilogram is the amount of weight at which 1 N of force will accelerate at a rate of 1 m/s2.)

A force is a vector quantity.

A vector quantity is a quantity which has both magnitude and direction.

Example: 10 Newtons, downwards 25 km, east

A scalar quantity can be described using only 1 quantity, magnitude.

Examples: time, energy, volume, temperature.