Acar starts moving from a traffic light on a highway with a constant acceleration of 2.5 m/s^2. the speed limit is 65 miles/hour. calculate the time from the start, when the car will exceed the speed limit, assuming that it keeps accelerating (in seconds).

After 11.62 sec car will axceed the speed limit  

Explanation:

We have given constant acceleration

As the car starts from rest so its initial velocity u = 0 m/sec

Final velocity v = 65 miles/hr

We know that 1 mile = 1609 meters

And 1 hour = 3600 sec

So

From first equation of motion v = u+at

So

t = 11.62 sec

So after 11.62 sec car will axceed the speed limit

fgravity=10x10=100n case 1

fgravity=30x20=600n case 2

6 times more