OpenStax College Physics for AP® Courses, Chapter 7, Problem 8 (Test Prep for AP® Courses)

This is College Physics Answers with Shaun Dychko. If wind is blowing horizontally toward a car with an angle of 30 degrees from the direction of travel, the kinetic energy will decrease because here's a picture of that scenario where this wind is at an angle of 30 degrees toward the car with respect to the direction of travel, which is velocity of the car and there's a component of the wind that is opposite to the velocity of the car and therefore slowing it down and by slowing it down, it's going to decrease its kinetic energy because kinetic energy is proportional to the speed squared. So there's this component here of the wind v wind that is parallel to the direction of travel or anti-parallel to be more precise because it's in the opposite direction to the velocity of the car and so it's gonna reduce its kinetic energy so that narrows our options down to (c) or (d). And then we need to consider the picture, where the winds blowing at the car at a 135 degrees with respect to its velocity or its direction of travel and here's that picture blowing towards the car at an angle of 135 degrees with respect to the velocity of the car. And there's a component of this wind, which is parallel along with... in the same direction as the velocity of the car and so it's going to speed it up. So here's the velocity of the wind parallel component and it's going to increase its kinetic energy in this scenario. So the answer to this question is (c).