It is given that:
When the car is moving uniformly, time period of simple pendulum, T = 4.0 s
As the accelerator is pressed, new time period of the pendulum, T' = 3.99 s
Time period of simple pendulum, when the car is moving uniformly on a horizontal road is given by,
Let the acceleration of the car be a.
The time period of pendulum, when the car is accelerated, is given by:
On solving the above equation for a, we get: