1.  Jim is walking down the street with a speed of 3 m/s. An angry mob starts chasing him so he accelerates to 6 m/s in 2 seconds. What is Jim’s acceleration? Show ALL of your work. Given:Work: a= v i = v f = t= Formula:Answer:

3.  I can compare an object’s acceleration and velocity.

4.  When an object’s velocity and acceleration are in the same direction, the object is speeding up.  When an object’s velocity and acceleration are in the opposite direction, the object is slowing down.

5.  Negative acceleration does not necessarily mean the object is slowing down.  If the acceleration and velocity are both negative, the object is speeding up.  The word deceleration has the connotation of slowing down. ◦ This word will not be used in the text.

6.  A freely falling object is any object moving freely under the influence of gravity alone. ◦ Acceleration due to gravity is 9.80 m/s 2  It does not depend upon the initial motion of the object. ◦ Dropped – released from rest ◦ Thrown downward ◦ Thrown upward

7.  We will neglect air resistance.  Free fall motion is constantly accelerated motion in one dimension. ◦ Use model of a particle under constant acceleration  Objects in a free fall near the Earth experience constant acceleration.  Let upward be positive  Use the kinematic equations ◦ With a y = -g = -9.80 m/s 2 ◦ Note displacement is in the vertical direction

8.  Initial velocity is zero  Let up be positive  Use the kinematic equations ◦ Generally use y instead of x since vertical  Acceleration is ◦ a y = -g = -9.80 m/s 2  v i = 0  a = -g

9.  a y = -g = -9.80 m/s 2  Initial velocity = 0  With upward being positive, initial velocity will be negative.  v i ≠ 0  a y = -g

10.  Initial velocity is upward, so positive  The instantaneous velocity at the maximum height is zero.  a y = -g = -9.80 m/s 2 everywhere in the motion  v = 0  v i ≠ 0  a y = -g

11.  Initial velocity at A is upward (+) and acceleration is -g (-9.8 m/s 2 ).  At B, the velocity is 0 and the acceleration is -g (- 9.8 m/s 2 ).  At C, the velocity has the same magnitude as at A, but is in the opposite direction.  The displacement is – 50.0m (it ends up 50.0 m below its starting point).

12.  Air resistance will increase as it falls faster ◦ An upward force on the object  Eventually gravity will balance with air resistance  Reaches terminal velocity - highest speed reached by a falling object.

13.  Force of gravity is constant u air resistance increases as you speed up u until the force is equal u Equal forces, no acceleration u constant velocity terminal velocity

16.  If touching going in the same direction add the velocities  If touching going in opposite directions subtract the velocities

17.  If not touching going in the same direction subtract the velocities  If not touching going in opposite directions add the velocities.

18. 15 m/s + 1 m/s = 14 m/s A student walking down the aisle on a school bus while bus is in motion.

19. 15 m/s += 1 m/s16 m/s  A student walking up the aisle on a school bus while bus is in motion.

20.  Suppose you are on a train platform as the train rushes through the station without stopping. Someone on board the train is pitching a ball, throwing it has hard as they can towards the back of the train. If the train’s speed is 60 mph and the pitcher is capable of throwing at 60 mph, what is the speed of the ball as you see it from the platform?  a) 60 mph to the right  b) 120 mph to the right  c) 0 mph (not moving)  d) 60 mph to the left 60 mph Train 60 mph