Forces

Spring force is the force exerted by a spring when it is compressed or stretched.

Problems

An unstrechted spring of length 15.0cm stretches by 4.0cm when a mass of weight 6.0N is suspended from it. The spring does not exceed the limit of proportionality.
What is the total length of the spring when the weight of the suspended mass is 3.0N?

Usually more than one force acts on an object. When two or more forces act on an object, the combination of those forces give us the single force known as resultant force. It represents the net force acting on an object. When two forces are combined,

• the magnitude of the resultant force depends on the angle between the two forces.
• the maximum resultant force occurs when two forces act in the same direction.
• the minimum resultant force occurs when two forces act in the opposite direction.

Torque is a measure of force that causes rotation in a non-rotating object or changes the rate of rotation of a rotating object. It is also known as turning effect of force or moment of force or just moment.

$\mathrm{Moment}=\mathrm{Force}\times \mathrm{Perpendicular\; distance\; from\; the\; pivot}$