How much work is needed to increase the speed of a 2.4 kg cart from 6.0m/s to 10.0m/s?

Hello

1) The work W is calculated as the product between the force F applied to the cart and the distance d covered by the cart:


2) The force is the product of the mass  m of the cart and its acceleration a:

If we use this into the formula of the work, we get


3) The cart is moving by accelerated motion. For this kind of motion, we have the following relationship:

where  and  are the final and the initial velocity of the cart. 
Re-arranging we have


4) Therefore, we can subsitute  into the original formula of the work, and we get

Ibelieve the correct answer would be c.

The independent variable would be the fertilizer as it is what the dependent variable (the growth of grass) depends on.