Newton’s 2 nd Law of Motion F = ma

Second Law of Motion This law states the net force of an object is equal to its mass times acceleration The equation for Newton’s 2 nd Law of Motion states the following: F = ma or force = mass x acceleration Force is expressed in Newtons (N), mass in kilograms (kg) and acceleration in m/s 2

Mass, Force and Acceleration When you apply a force to an object, you cause object to accelerate by changing the speed or direction of the object The harder you throw a ball, the more it accelerates If you double the force on a ball, the acceleration will double also

Acceleration The acceleration of an object is always in the same direction as the net force If the net force acts in the opposite direction to the object’s motion then the force will produce a deceleration

Force Example – solving for acceleration A car with a mass of 1000kg accelerates when the traffic light turns green. If the net force on the car is 4000N, what is the car’s acceleration? m = 1000kg, F = 4000N F = m x a so a = force/mass A =4000N/1000kg = 4m/s 2

Force Example – solving for force A car with a mass of 1200kg accelerates at a rate of 3.0m/s 2. What is the net force acting on the car? m = 1200kg, a = 3.0m/s 2 F = ma so F = 1200kg x 3.0m/s 2 = 3600N

Force Example – solving for mass A 25N force accelerates a boy in a wheelchair at 0.5m/s 2. What is the mass of the boy and the wheelchair? F = ma so m = F/a F = 25N, a = 0.5m/s 2 m = 25N/0.5m/s 2 = 50kg