SPH 4U1
Physics Grade 12
Unit 2: Kinematics (How Things Move)
Note 3: Acceleration & Acceleration Due to Gravity
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Reference Text Sections 1.2, 1.3
Recall Definitions:
Acceleration – rate of change of velocity
Instantaneous Acceleration – acceleration at one point in time
DEMO: heavy and light objects accelerating at same speed. Discuss Aristotles’ mistakes and Galileo’s discovery….
Gravity – force of attraction between masses
Acceleration Due to Gravity – Approx. 9.8 m/s2
Free Fall – motion of an object falling to earth with only gravity acting on it.
Terminal Speed – Air resistance becomes so great that there is no more acceleration.
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Solving Constant Acceleration Problems (the formulas to use J):
These can be derived from Velocity vs Time graph
Example 1:
Find a baseball’s acceleration if the pitcher’s wind up is 3m and the speed is 50 m/s.
Solution: 
Rearrange 
Example 2:
A steel ball is thrown from the ledge of a building so that it has an initial velocity of magnitude 15.0 m/s. The ledge is 15.0 m above the ground (assume no air resistance).
a) What are the total flight time and the speed of impact at the ground if the initial velocity is upward? (Answer: flight time = 3.86 s, impact speed = 22.8 m/s)
b) What are these two quantities if the initial velocity is downward?
(Answer: flight time = 0.8 s, impact speed = 22.8 m/s)
c) Based on your answers to a) and b), write a concluding statement.(Answer to this will be the final velocity is independent of whether the ball is thrown up or down)
Example 3:
Car A is traveling at 11 m/s [N] when it passes a stationary Car B. When A is 20m ahead of B, B begins to accelerate at a uniform rate of 4.0 ms-2 [N] and at the instant, A begins to accelerate at a uniform rate of 2 ms-2 [S]. Determine when and where B catches up with A.