1 st Semester Exam Review

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

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 to scientific notation Example: change 4.12 x 10 6 to standard form

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

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

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

a = v f - v i t d = v i t + ½ at 2 v f 2 = v i 2 +2ad

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).

When an object is in free fall, its acceleration is -9.8 m/s 2. The entire time the object is in free fall its acceleration is -9.8 m/s 2 even when the object is moving up.

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

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

Vector Addition

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)

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

Projectiles Projectiles move at constant velocity in x direction Projectiles have acceleration -9.8 m/s 2 in y direction Time for a falling object is the same as time for an object to hit the ground if fired horizontally.

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 2 nd Law: F net = ma Newton’s 3 rd Law: For every force there is an equal and opposite force

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.

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

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)

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

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 = m Δ v

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

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.

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

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