F=ma

==Newtons Second Law== An object will only '''accelerate''' if there is a '''net''' or '''unbalanced force''' acting upon it. The acceleration of an object is dependent upon two variables - the net force acting upon the object and the mass of the object. ===[image:http://i.imgur.com/ePH6IIr.png?1]=== The forces are unbalanced. There is a net forces that causes the car to '''accelerate''' forward. ===[image:http://i.imgur.com/jbHXa20.png?2]=== If the net force is acting in the opposite direction to the velocity of an object it will cause the object to decelerate (slow down). If you label the velocity as being in the positive direction, this can also be described as negative acceleration. ===Newtons second law can also be expressed using the following formula:=== [image:http://i.imgur.com/04yW9B6.png?1] [image:http://i.imgur.com/wDibmDk.png?1] '''''Note: Newton's Second Law actually states that a net force is equal to the rate of change of an object's momentum but we can rearrange this expression into the familar form of F = ma.''''' ==Worked example== [image:http://i.imgur.com/GBRTrXK.png] A force of 100N is applied to empty shopping trolley with a mass of 20kg. Calculate the resulting acceleration. '''a = F ÷ m''' = 100 ÷ 20 = 5ms^-2^ What is the acceleration when the shopping trolley is full and has a mass of 50kg? '''a = F ÷ m''' = 100 ÷ 50 = 2ms^-2^