Average Acceleration Formula: Definition, Equation and Calculation

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Average acceleration is defined as the rate of change of the velocity of the object and is given by the following equation. In the real world, everything is always in motion. Objects move at a variable or a constant speed. When someone steps on the accelerator or applies brakes on a car, the speed of the car increases or decreases and the direction of the car changes. In physics, these changes in velocity or directional magnitude of a moving object are represented by acceleration. 

Keyterms: Acceleration, Velocity, Motion, Straight Line, Speed, Magnitude, Time, Interval of time, Circular orbit, Centripetal acceleration

Read More: Motion in a Straight Line


What is Average Acceleration?

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The rate of change of velocity is known as acceleration. It is indicated by "a" and is measured in units of m/s2. Average acceleration is defined as the change in velocity at a particular interval of time. Unlike acceleration, the average acceleration at a particular interval is calculated. 

Average Acceleration
Average Acceleration

Velocity is a vector quantity, having both direction and magnitude. If any of these change over a while, there is acceleration. An object with a constant (constant) velocity in a circular orbit can have a satellite-like acceleration around the earth that moves in a constant motion but experiences a kind of acceleration called centripetal acceleration.

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Average Acceleration Formula

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Average acceleration is calculated according to the following formula. 

\(a = \frac{v - v_0}{t} = \frac{ \Delta v}{\Delta t}\)a is average acceleration, Δv is change in velocity and Δt is change in time.

The change in velocity is Δv and Δt is the total time the speed changes. where,

The final velocity is Vf

The initial Velocity is Vi

The initial time is Ti

The final time is Tf

If the object also shows different velocities such as v1, v2, v3 ... vn at different time intervals such as t1, t2, t3 ... t3, the average acceleration is calculated according to the following formula:

In other words, the average acceleration is defined as the rate of change of the velocity of the object and is given by the following equation.

Average Acceleration = Change in velocity/Time Elapsed

The unit of acceleration is meters/second square.

Since the velocity change Δv occurs at a finite time interval Δt, it is necessary to define the average acceleration. When the time interval becomes infinitely small, there is immediate acceleration or short acceleration, which is given by the following equation.

Average Acceleration Formula
Average Acceleration Formula

When the object moves in a straight line, the magnitude of the velocity vector is only partly because there is no change in direction in this case. Therefore, the direction symbol can be omitted.

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Things to Remember

  • The rate of change of velocity is known as acceleration. It is indicated by "a" and is measured in units of m/s2.
  • Unlike acceleration, the average acceleration at a particular interval is calculated. Velocity is a vector quantity, having both direction and magnitude.
  • An object with a constant (constant) velocity in a circular orbit can have a satellite-like acceleration around the earth that moves in a constant motion but experiences a kind of acceleration called centripetal acceleration.
  • The average acceleration is defined as the rate of change of the velocity of the object and is given by the following equation. Average Acceleration = Change in velocity/Time Elapsed. The unit of acceleration is meters/second squared.

Previous Years’ Questions


Sample Questions

Ques: The bus accelerates at an initial velocity of 10 m / s for 5 seconds, then at 20 m / s for 4 seconds, and finally at 15 m / s for 8 seconds. What can you say about the average acceleration of the bus? (3 marks)

Ans: Bus velocities at various time intervals are v1 = 10 m / s, v2 = 20 m / s, v3 = 15 m / s.

The time intervals for objects to have these velocities are t1 = 5s, t2 = 4s, t3 = 8s.

Therefore, the total velocities during the interval can be given as the sum of these velocities.

Similarly, the total time interval can be given as the sum of these intervals.

Ques: A sparrow accelerates from 3 m / s to 6 m / s in 5 seconds while returning to the nest. What can you say about that average acceleration? (3 marks)

Ans: Given: Initial velocity, vi = 3 m / s

Final velocity, vf = 6 m / s

Total time for acceleration, t = 5 seconds

Ques: The car drives in a straight line for 10 seconds along the freeway at a constant speed of 8080 mph. Find its acceleration. (3 marks)

Ans: The average acceleration is the change in velocity divided by the time required. Since the speed (size and direction) of the motor is constant during riding, it is defined as zero average acceleration.

Ques: A friend's new car can go from 0 to 60 m / s in 7 seconds. What is acceleration? (4 marks)

Ans: Final speed, vf = 60 m / s; Initial speed, vi = 0; Last time, tf = 7 seconds. And the first time, ti = 0.

Aavg = Δv / Δt

Average = (60 m / s) / 7 seconds

Average = 12.86 m / s2

Ques: If you drive on the sidewalk at 45 m / s, you will see the child running down the street and rapidly decelerating to 3 m / s in 1.5 seconds. What is your gear? (2 marks)

Ans: Final velocity, vf = 3 m/s; initial velocity, vi = 45 m / s; time t = 1.5 seconds.


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CBSE CLASS XII Related Questions

  • 1.
    Derive the relation for the refractive index ($\mu$) of a prism in terms of angle of minimum deviation ($\delta_m$) and angle of prism ($A$).

      • $\mu = \frac{\sin\left(\frac{A + \delta_m}{2}\right)}{\sin\left(\frac{A}{2}\right)}$
      • $\mu = \frac{\cos\left(\frac{A + \delta_m}{2}\right)}{\cos\left(\frac{A}{2}\right)}$
      • $\mu = \frac{\sin\left(\frac{A - \delta_m}{2}\right)}{\sin\left(\frac{A}{2}\right)}$
      • $\mu = \frac{\tan\left(\frac{A + \delta_m}{2}\right)}{\tan\left(\frac{A}{2}\right)}$

    • 2.
      The electron drift speed is estimated to be only a few mm/s for currents in the range of a few amperes. How, then, is the current established almost the instant a circuit is closed ?


        • 3.
          A student sets up the circuit as shown in the figure to find the value of unknown resistance X and records a set of readings of the voltmeter and the ammeter by using the rheostat.


            • 4.
              The assertion that V = IR is a statement of Ohm’s law is not true. Why ?


                • 5.
                  A low voltage supply from which one needs high currents must have very low internal resistance. Why ?


                    • 6.
                      Obtain an expression for the work done to dissociate the system of three charges \(q\), \(-4q\) and \(2q\) placed at the vertices A, B and C respectively of an equilateral triangle of side \(a\).

                        CBSE CLASS XII Previous Year Papers

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