Chapter 2-3 Newton’s Second Law

How do forces change motion? Changing the object’s: Speed Direction Both

Velocity Velocity: Speed in a given direction Hurricane 3

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Unbalanced Forces on an Object at Rest If the object moves – the forces are unbalanced Moves in direction of net force

Unbalanced Forces on an Object in Motion Speeding up Slowing down Changing direction Acceleration (speed and direction)

Newton’s Second Law The amount of force acting on an object equals the object’s mass times its acceleration. 7

Newton’s 2nd Law Force = Mass x Acceleration F = M x A A = F / M M = A / F Newton (N) – Unit of measurement for Force 1 Newton = 1 kg x 1 m/s² 8

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Newton’s 2nd Law If you throw a softball and a baseball as hard as you can, why don’t they have the same speed? 10

2nd Law Practice What is the acceleration of a boy on a skateboard if the unbalanced forward force on the boy is 15 N? The total mass of the boy and the skateboard is 58 kg. What force is necessary to accelerate a 1250 kg car at a rate of 40 m/s2? What is the mass of an object if a force of 34 N produces an acceleration of 4 m/s2? 11

Circular Motion Example – 20 m/s to the north Circular Motion – May have same speed, but not the same velocity 12

Centripetal Force Force that acts perpendicular to the direction of motion Goes towards center of curve

Satellites and Planet Motion Moves in straight path – inertia Gravity pulls object inward – centripetal force