Problem:
A car is retarded by applying brakes at the rate of 2m/s. It is finally stopped in 10s. Find its initial velocity.

Solution:

To find the initial velocity of the car, we need to use the formula:

v = u + at

Where:
- v is the final velocity (which is 0 in this case since the car is stopped)
- u is the initial velocity (the value we need to find)
- a is the acceleration (given as -2m/s since the car is being retarded)
- t is the time taken (given as 10s)

Substituting the values into the formula:

0 = u + (-2m/s) * 10s

Simplifying the equation:

0 = u - 20m/s

To isolate u, we can rearrange the equation:

u = 20m/s

Answer:
The initial velocity of the car is 20m/s.

Explanation:
When the brakes are applied to a moving car, it experiences a negative acceleration (retardation) which causes it to slow down. The rate of this retardation is given as 2m/s. The car comes to a stop after a time of 10s. To find the initial velocity, we use the equation v = u + at, where v is the final velocity, u is the initial velocity, a is the acceleration, and t is the time taken. Substituting the given values into the equation, we get 0 = u - 20m/s. Rearranging the equation, we find that the initial velocity of the car is 20m/s.

20m/s