<span>2.56 sec (t=1/0.39)
f=3.9/10</span>
Answer:
a) Option D
b) Option A
Explanation:
a) Option D
Because a massive car will have more inertia which will make the car move faster but a massive car simultaneously will have more friction thereby restricting its movement in the forward direction. Hence, all the three cars will move equal distance.
b) Option A, Car F
Being most massive car, the frictional force required to stop the car will be highest.
Explanation:
The Coulomb's law states that the magnitude of each of the electric forces between two point-at-rest charges is directly proportional to the product of the magnitude of both charges and inversely proportional to the square of the distance that separates them:

In this case we have an electron (-e) and a proton (e), so:

In this case, the electric force is negative, therefore, the force is repulsive and its magnitude is:
