Newton’s second law

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Newton’s second law

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

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