Answer:

Explanation:
The potential energy of the spring or the work done by the spring is given by :
............(1)
k is the spring constant
d is the compression
When the spring is compressed a distance d' = d/3, let W' is the work is required to load the second dart. Then the work done is given by :

.............(2)
Dividing equation (1) and (2) :



So, the work required to load the second dart compared to that required to load the first is one-Ninth as much. Therefore, the correct option is (E).
To score in the correct goal
Force applied on the car due to engine is given as
towards right
Also there is a force on the car towards left due to air drag
towards left
now the net force on the car will be given as

now we can say that since the two forces are here opposite in direction so here the vector sum of two forces will be the algebraic difference of the two forces.
So we can say



So here net force on the car will be 150 N towards right and hence it will accelerate due to same force.