Presentation Transcript

1. Newton’s Second Law: Force and Acceleration

   8SCIENCE
2. Newton’s Laws Newton’s first law of motion describes motion of an object with NO net force That an object will stay at rest or stay in constant velocity (unless acted on by an outside force) Newton’s second law of motion: An object affected by a net force will accelerate in the direction of the force Ex. If an object like a ball is kicked forward, it will move faster in a forward direction
3. Newton’s second law of motion Acceleration = net force mass a = __F__ m F = force measured in Newtons (1 N = kg · m/s²) If force acts on a small mass and a large mass, the small mass will accelerate more Ex: if you try to push an empty box across the floor, it will accelerate faster if the box is packed with books
4. Calculate the dogs’ acceleration Remember: a = f/m where a = acceleration, f = force and m = mass
5. Balanced/Unbalanced Forces If you are sitting, you are at rest: all the forces are balanced (you are not moving) Gravity is pulling you down, chair is pushing you up The upward force of the chair surface is called the normal force It is straight up and balances your weight If you put a heavy weight on the chair, it may no longer have enough normal force and the chair may break Also, if the surface becomes tilted (ex. Like a ramp/incline) the normal force can no longer balance this weight and you move downhill
6. Unbalanced forces **Remember: When forces acting on an object are not balanced, it accelerates in the direction of the net force What is an object doing if it positively accelerates? Negatively accelerates? It may speed up, slow down or turn Ex. Turning: if you jump off a diving board into a pool you will not continue straight across the pool at that height - gravity will cause you to turn and accelerate downwards