1. ACCELERATION

2. Acceleration Acceleration is change in velocity over time. a = vf - vi
If vf > vi, a is +……this is acceleration
If vf < vi, a is -……this is deceleration or
(-)acceleration

3. v vs. t graphs Slope = v/t = a
What is the average acceleration over the first 40s?
Area under the curve gives displacement
v x t = m/s x s = m
How far did the object travel in 40s?

4. Uniform Acceleration
An object speeds up or slows down at a constant rate.
Displacement depends upon initial velocity, acceleration, and time.
Final velocity depends on initial velocity, acceleration and time.
To solve for these unknowns, we use the 3 main Kinematics Equations

5. Equations using Acceleration
vf = vi + at
d = vit + 1/2at2
vf2 = vi2 + 2ad
Be sure to use the equation that you have the most known information for and includes the variable you are looking for.

6. Working in 2 Dimensions
When we are talking about a car or or other object traveling on the ground, we are working on the horizontal plane.
We can also use these equations in a vertical plane.
In a vertical plane, acceleration is due to gravity. More to come later.

7. Try These
A car accelerates from 4m/s to 20m/s in 4s. What is the acceleration?
A car starts from rest accelerates 5m/s2 over 30m. What is the final velocity of the car?
A car slows from 40m/s to a stop in 5s. What is the acceleration?
If an object starts from rest and accelerates 10m/s2 for 2s. How far will it travel?

8. Gravity

9. Gravity
Galileo discovered that by neglecting the effects of air, all objects falling had the same acceleration.
This value is “g”
Or -9.8m/s2
Different places around the world have different values of g.

10. g g is known as the acceleration due to gravity.
Because gravity accelerates objects in a downward direction, g is a negative acceleration.
This is due to the fact that acceleration is a vector.
GLOC

11. How does gravity affect things?
Depends upon your reference point.
If a stone drops from the top of a building: after 1 second it will be traveling -9.8m/s downward and after 2 second it will be traveling
-19.6 m/s.
If a ball is thrown upward gravity will slow the ball down and then the ball will accelerate back down.
Time up = time down

12. Practice A brick is dropped from a high scaffold.
What is it’s velocity after 4.0s?
How far does the brick fall during this time?

13. More Practice
A tennis ball is thrown straight up with an initial speed of 22.5m/s. It is caught at the same distance above ground.
How high does the ball rise?
How long did the ball remain in the air?

14. A ball is thrown up with an initial velocity of 29. 4 m/s
A ball is thrown up with an initial velocity of 29.4 m/s. How much time does it take for the ball to stop rising?

15. A stone is dropped from the top of a cliff and hits the ground 3 seconds later. Find
a) the magnitude of the velocity at which the stone hit the ground
b) the distance that it fell.

16. A person standing on top of a building throws a ball downward at 5m/s
A person standing on top of a building throws a ball downward at 5m/s. Find
The velocity it is traveling in 3.0s
The distance it travels in 3.0s