Newtons Second Law
Unbalanced Forces

Newtons second law of motion essentially states that if an unbalanced force acts upon a body it will accelerate the body in the direction of the force with a magnitude equal to mass x acceleration.
The formula: 


helps us to apply the law. F stands for "force", m stands for "mass" and a stands for "acceleration".

Our Top Gift Ideas for Young Scientists

This law tells us how much force is needed to accelerate a mass. Say for example we have two weights and we shoot them out of an air canon. If weight 1 is half the weight of weight 2 we can predict using F=ma that weight 1 will accelerate at twice the speed of weight 2. This means that the less mass something has the less force it takes to accelerate it.

A good example of this would be to suspend a pistol in mid air and then fire it. The bullet would shoot out of one end with killing potential. The gun having 100 times more mass would fly in the
other direction with the same amount of force, but with less lethality and 100 times less speed.

Newtons second law applies to objects here on earth and in outer space. As long as an object does not come close to approaching the speed of light this law holds. If an object starts to approach the speed of light Einstein’s special theory of relativity must be used. These rules
apply in outer space where there is no immediate apparent gravitational force.

All objects have mass which means even in outer space it would take more force to accelerate a car than a baseball up to the same speed, so Newtons second law would still apply. Here on earth in everyday life we use the term weight, but the word mass is not so commonly used. The
difference between mass and weight is that the mass of an unaltered object cannot change, although its weight on the other hand will change in relation to the object’s surroundings. Weight is just basically the amount of force gravity exerts on a mass. If you fly an object into
outer space, it will go from weighing, say, 1 kg to being nearly weightless. Though mass on the other hand, will not change as it is in direct relation to the amount of matter the object consists of.

Force is measured in using Newton. One Newton is equal to the amount of force needed to give 1kg an acceleration of 1m/s2. Force is a vector meaning it not only has magnitude, but also direction.

Return to home

Go back from "Newtons Second Law" to home.