A vehicle is moving at a speed of 20m/s suddenly the driver sees a fallen tree on the road, he instantly applies the brakes that subject the car to a deceleration of -2m/s².Find a) Time required by the car to stop.
b) distance covered before stopping.

b) Distance covered before stopping.

Explanation:

If you want to find the distance d required to come to a stop starting at some initial speed v, with braking acceleration a, use the kinematic relation  

vf2 - vi2 = 2ad

vi = initial speed at the moment braking begins = v

vf = final speed = 0 (comes to a full stop)

-v2 = 2ad

d = -v2/(2a)

the working equation for the angular size is the product of the physical size and 360 degrees divided by the product of two pi and distance from earth. the minimum size would be 0.559 degrees while the maximum size would be 0.49 degrees. 

number of electrons for neutral cl