1 / 12

COLLISIONS & KINETIC ENERGY

COLLISIONS & KINETIC ENERGY. Two identical carts with opposite velocities. Case 1 One cart has a spring attached. Result: elastic collision -no loss of energy. Case 2 One cart has clay attached to stick.

tameka
Download Presentation

COLLISIONS & KINETIC ENERGY

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. COLLISIONS & KINETIC ENERGY Two identical carts with oppositevelocities. Case 1 One cart has a spring attached. Result: elastic collision -no loss of energy. Case 2 One cart has clay attached to stick. Result: Completely inelastic collision -all energy lost. If some energy is lost then - inelastic

  2. COLLISIONS CONTINUED Case 3. One cart is at rest and has potential energy stored in a spring. When the second cart collides, the stored energy is released and both carts share the stored energy that was released. Similar to a slingshot effect or gravity assist when a satellite (or spacecraft) overtakes a planet. See Figure 3-34

  3. Power Power is the rate at which energy is transferred or transformed. Power = Work (or Energy used) time Symbol: P Unit: watt = Joule/ second (w)

  4. Power • Thus the numerator can have several forms: • Work = F * d • Energy used could be: KE = 1/2 m v2 • could be: PE = mgh • could be: ELOST = ffriction d • could be: PE = 1/2 k x2

  5. POWER UNITS Metric English watt foot-pound horsepower second Conversions 746 watts = 550 ft-lb/sec = 1 horsepower

  6. Power • A person runs up to the third floor in 15 s. • If the person has a weight of 580 N and each flight is 4 m, how much power does the person generate ? • G t = 15.0 s, W = 580 N, h = 2*4.0 m • U P (watts) = ? • R P = Work (or energy used) /t • = mgh/t = W h/t

  7. Power • U N * m/s = W • C P = 580 N * 8.0 m/ 15.0 s • A P = 309 W

  8. Power • Suppose a car moves on the highway due to a force of 500 N on the wheels which moves the car at a speed of 30 m/s. What is the power being delivered to the wheels? • G F = 500 N • v = 30 m/s • U P (watts)

  9. Power • R P = Work done (energy used)/time • U N m /s = W • C Work done = F * d/t • R but v = d/t • C P = F* v = 500 N * 30 m/s • A P = 15 kW

  10. ROTATIONAL MOTION Linear Motion Rotational Motion d (distance)  (angle) radian (rad) v (velocity) (angular velocity) rad/s a (acceleration)  ( ang. acceleration) rad/s2 m ( mass) I ( moment of inertia) F = m a  = I  mv (momentum) I (angular momentum)

  11. Relationship of Linear to Angular d = r  v = r  a = r  (small mass) I = m r2

  12. CONSERVATION OF ANGULAR MOMENTUM The total angular momentum of an isolated system is a constant. (I )before = (I )after For a small spherical object of mass m Sum (m v r) before = Sum (m v r) after

More Related