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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?.
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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 a m 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/s, what force did you exert on the ball.
Solving for Force • You throw a ball to a friend. If the ball has a mass of0.15kg and it accelerates at 20m/s, 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