Acceleration is change in velocity / time.
On the graph mark a point at which we want to find acceleration.
P {x= a, y =b}. a gives the time and b gives the velocity at that instant of time.
On the x axis with a as center, mark two points left and right of ‘a’ such that the interval between the two points is one second.
In other words, mark on the x axis two points [a + 0.5] and [a – 0.5].
Time interval between the two points is now 1 s.
Next corresponding to the point [a + 0.5] find the velocity from the graph.
Similarly find the velocity corresponding to the point [a – 0.5].
The difference between the two values gives directly the acceleration at the point [a, b] since the time interval is one s.
Instead of taking time interval as one second, one can take still smaller value of time.
But in this case, we must divide the velocity difference by the time value.
Smaller the time value, greater is the accurate result for acceleration.
Repeat the procedure for other points also.