Question

A car’s speedometer reads 20 m/s after accelerating, from a standing start, for 25s. What was the magnitude of its acceleration?

Answer 1

Magnitude of acceleration = (change in speed) / (time for the change)

Change in speed = (speed at the end) - (speed at the beginning)

                         =             (20 m/s)    -        zero

                         =          20 m/s

Time for the change  =  25 s

Magnitude of acceleration =  (20 m/s) / (25 sec)

                                       =    (20/25)  m/s²

                                       =      0.8 m/s²  

Answer 2

A car’s speedometer reads 20 m/s after accelerating, from a standing start, for 25s. The magnitude of the car's acceleration is 0.8 m/s².

Acceleration can be defined as the change in the velocity of an object over an extended period of time. An object's acceleration is brought by a given amount of force which can either be through a push or a pull.

Given that:

• a car's speedometer accelerates with a given velocity of 20 m/s from rest
• the time taken t = 25s

Using the first equation of motion

• v = u + at

where;

• v = final velocity
• u = initial velocity
• a = acceleration
• t = time

Making acceleration (a) the subject of the formula; we have:

v - u = at

$\mathbf{a = \dfrac{v - u}{t}}$

here;

• v = 20 m/s
• u = 0 m/s
• t = 25 s

$\mathbf{a = \dfrac{(20 - 0) \ m/s}{25 \ s}}$

$\mathbf{a = 0.8 \ m/s^2}$

Therefore, we can conclude that the magnitude of the car's acceleration is 0.8 m/s².

Learn more about acceleration here:

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