1 st Semester Exam Review

1. 1st Semester Exam Review

2. Math and Metrics Sig Fig Rules: 505 – zero is significant 500 – zeroes not significant 0.05 – zeroes not significant 5.00 – zeroes significant 0.0500 – only zeroes at the end are significant Most commonly missed rule: zeroes that are after the decimal and are final zeroes are significant

3. Math and Metrics Be able to convert (m/skm/h) (mcm), etc Be able to convert from standard form to scientific notation and vice versa Example: change 0.0002490 to scientific notation Example: change 4.12 x 106 to standard form

4. Linear Motion What is the distance? What is the displacement?

5. Speed vs Velocity • Speed = scalar • Velocity = vector S = total distance / total time V = displacement / total time

6. Acceleration • The rate of change of velocity • All acceleration we have studied has been constant • + v and + a = speeding up • + v and – a = slowing down • - v and + a = slowing down • - v and – a = speeding up

7. a = vf - vi t d = vit + ½ at2 vf2 = vi2 +2ad

8. Free Fall • An object is considered in free fall when it is moving only under the influence of gravity. • An object that is thrown up in the air is in free fall (even when it is moving up).

9. When an object is in free fall, its acceleration is -9.8 m/s2. • The entire time the object is in free fall its acceleration is -9.8 m/s2 even when the object is moving up.

10. Graphing • Know how to draw graphs of: d vs t; v vs t; a vs t For object: At rest Constant speed Speeding up Slowing down Dropped Thrown up and comes back down

11. Graphing • Be able to identify what v vs t graph belongs to what d vs t graph

12. Vector Addition

13. Vectors Know how to add vectors in the same direction, in opposite directions and at right angles. Be able to find components of a vector (i.e. sides of a triangle)

14. Vectors S = d/t can be used with vectors You must match up speed and distance

15. Projectiles • Projectiles move at constant velocity in x direction • Projectiles have acceleration -9.8 m/s2 in y direction • Time for a falling object is the same as time for an object to hit the ground if fired horizontally.

16. Forces • Newton’s 1st Law: Object in motion stays in motion, object at rest stays at rest UNLESS acted on by an outside force (also called law of inertia) • Newton’s 2nd Law: Fnet = ma • Newton’s 3rd Law: For every force there is an equal and opposite force

17. Forces • Force is not needed to maintain motion. • Object with zero net force is in equilibrium • Object in equilibrium will have no change in its motion (either at rest or in motion at a constant speed) • Inertia is not a force. It is the tendency of an object to resist a change in its motion.

18. Forces • Inertia is directly proportional to mass (more mass, more inertia)

19. Forces • Problem solving: Basic: net force given? Fnet = ma Advanced: multiple forces acting (i.e. tension and weight, or Fapp and Friction) draw FBD and write equations (U-D = may) (R-L = max)

20. Force • More Problem Solving Equilibrant force: use pythagorean theorem to find resultant force equilibrant force is same value 180 degrees in other direction

21. Momentum • P = mv • J = Ft • Momentum is changed when an impulse acts on an object. • The impulse is equal to the change in momentum. • Ft = mΔv

22. Momentum • Vector quantity • Always conserved in a closed system (no outside forces presenti.e. friction)

23. Momentum • Consequence of Impulse-Momentum Theorem: if time of collision is extended, force will decrease. • Extending time has NOTHING to do with the change in momentum, also can’t change the value of impulse.

24. Momentum • Inelastic: objects collide and stick together • Elastic: objects collide and bounce apart • Momentum is conserved in both types of collisions

25. Concept Questions • When you do throw that bowling ball while standing on the pond: How does your final velocity compare to that of the ball? How does your final momentum compare to that of the ball? Assume no friction Ans: The ball has a greater velocity, you have equal momentum