This document defines acceleration and discusses how it relates to changes in an object's speed or velocity over time. It provides the formula for calculating acceleration as the change in velocity divided by the elapsed time. Examples are given of cars accelerating on highways and decelerating in traffic or while turning. Graphs of velocity versus time are used to illustrate constant acceleration, zero acceleration (constant velocity), and deceleration. Sample problems calculate the acceleration of vehicles speeding up or slowing down uniformly over time.

1. Changing speed and velocity:

2. How do you describe that a car or
object changes its speed or velocity?
• When it slows down
• When it speeds up
In what situations or places where cars happen to
change the speed?
• When it is travelling in a high way its speed increases.
• When it travels in a traffic road the speed decreases
• When it turns a curve path the car also slows down.

3. What do you call this rate of change
in velocity of the object?
• It is called acceleration.
• In formula we can write acceleration as:
• Acceleration= change in velocity
•
elapsed time
• In symbol:
• a = Δv or a = vf - vi
Δt
tf - ti

4. Vf is final velocity , vi is initial velocity
tf is final time
, ti is initial time
What is the MKS unit of acceleration?
The MKS unit of acceleration is meter per
second squared, in symbol m/s². Other unit is
the km/h²

5. Application:
• Solve the given problems:
• 1. A car on a straight level road is stopped for
a red light. On the green light, it uniformly
accelerates to a velocity of 18m/s in 3
minutes. What is its acceleration?
• A jet plane flying at 100m/s is uniformly
accelerated to a cruising speed of 150m/s in
20 minutes. What is its acceleration during
this time?

6. Reinforcement:
• Which of the following is a graph of
acceleration?
• A.
B.
C.
v
v
v
t
t
t
Answer:
All of them show a graph of acceleration.
Why?

7. • 2. How do you describe the slope of graph
A? graph B? Graph C ?
Answer:
Graph A has a positive slope
Graph B has zero slope
Graph C has negative slope
3. What does a positive slope mean? A zero
slope? A negative slope?

8. • Answer:
• Positive slope means it has a constant
acceleration, the velocity changes but at
constant rate.Constant acceleration is also called
uniformly accelerated motion.
• Zero slope means no acceleration but the car
is still moving with constant velocity.
• Negative slope means the acceleration is
constant at decreasing velocity, when the
velocity decreases its called deceleration.

9. Analyze the following graphs of
acceleration
• A.
B.
C.
v
v
v
t
t
Which graph shows constant acceleration?
Answer: All of them
Which graph shows highest or greatest
acceleration?
Answer: graph A, why?
t