Newton’s Second Law Acceleration

Effect of Force If there is a net force on an object, the object accelerates. If you push harder, you get more acceleration Acceleration is directly proportional to the net force

What does Directly Proportional Mean? If force increases, acceleration increases If force decreases, acceleration decreases Ex. If the force doubles, so does the acceleration. (the harder you push, the faster it moves)

Direction of force and acceleration Acceleration acts in the same direction as the net force. Ex. As the boy pulls the wagon towards him, it speeds up in his direction.

Mass and Acceleration A force applied to an automobile will not have the same effect as the same force applied to a pencil. An automobile resists accelerating much more than a pencil does, because it has more inertia, or mass. The acceleration of an object depends not only on how hard you push on it, but also on how much the object resists being pushed.

Effect of Mass For the same force, an object with twice the mass will have half the acceleration. If it had three times the mass, the same force will produce one-third the acceleration and so on. Acceleration is inversely proportional to mass

What does Inversely Proportional Mean If mass increases, acceleration decreases If mass decreases, acceleration increases

Newton’s Second Law In symbols: F a = F m m a F = ma

Solving for Force You throw a ball to a friend. If the ball has a mass of 0.15kg and it accelerates at 20m/s2, what force did you exert on the ball.

Solving for Force You throw a ball to a friend. If the ball has a mass of 0.15kg and it accelerates at 20m/s2, what force did you exert on the ball. F = m x a F = 0.15 x 20 = 3N

Solving for Acceleration You throw a 0.5 kg ball with a force of 10N. What is the ball’s acceleration

Solving for Acceleration You throw a 0.5 kg ball with a force of 10N. What is the ball’s acceleration M = 0.5 F = 10 N Acceleration = A A = F/m =10 N / 0.5 kg = 20m/s2

Solving for Mass What is the mass of a water skier that is accelerating at 2.0 m/s2 while being pulled with a force of 110N.

Solving for Mass What is the mass of a water skier that is accelerating at 2.0 m/s2 while being pulled with a force of 110N. M = F A = 110 N 2.0 m/s2 = 55 kg