In which one of the following situations is zero net work done? a) a ball rolls down an inclined plane. b) a physics student stretches a spring. c) a projectile falls toward the surface of earth. d) a box is pulled across a rough floor at constant velocity. e) a child pulls a toy across a rough surface causing it to accelerate.

Option D

Explanation:

The work done can be given by the mechanical energy used to do work, i.e., Kinetic energy and potential energy provided to do the work.

In all the cases, except option D, the energy provided to do the useful work is not zero and hence work done is not zero.  

In option D, the box is being pulled with constant velocity, making the acceleration zero and thus Kinetic energy of the system is zero. Hence work done in this case is zero.

the expression 15n + 2(3p) represents the amount isaiah spent buying gasoline and snacks, where n represents the price of each gallon of gasoline and p represents the cost of each snack that he bought. which statement is true about the amount isaiah spent?

yup its correct its: c) b b