Kaplan 10th Edition DT Q19

Kaplan's Book

19) This question asks us to find the magnitude of the force pushing on a car. The car starts at rest and ends with a kinetic energy of 18,000 J. Additionally, we know that the car is pushed for 30 meters. This question can be solved in multiple ways. One of the easier ways is to use energy and work. The problem doesn't mention frictional force, drag force, or any other non-conservative force. So we can solve the problem using only the work done by conservative forces.

Where W is work, F is force, d is displacement, K is kinetic energy, and U is potential energy

Considering the given values, we want to use the blue and orange equation.

Our next step is the find the change in kinetic energy. We are already given that the kinetic energy at the end is 18,000 J. We are also told that the initial velocity is 0. We can solve for the initial kinetic energy, then solve for the change in kinetic energy

Where m is mass, v is velocity, and K is kinetic energy

Now, we can set up an equation for the net work and solve for the force.

Where W is work, F is force, d is displacement, and K is kinetic energy

Answer: B