On a downgrade, your vehicle is working _____ gravity, resulting in a(n) _____ in speed.

On a downgrade, your vehicle is working _____ gravity, resulting in a(n) _____ in speed.

• A. Against gravity, decrease
• B. Against gravity, increase
• C. With gravity, decrease
• D. With gravity, increase

Answer: (D)

Gravity's effect on speed when moving downhill is the key idea. On a downgrade, gravity pulls the vehicle downhill along the slope, so the component of gravitational force acts in the direction of travel. This adds energy to the motion, converting potential energy into kinetic energy, which tends to increase speed if you don’t brake. In other words, you’re working with gravity, not against it, so speed rises as you descend. Of course, braking or engine braking can counter this and keep speed in check, but without braking the vehicle would accelerate. The other options imply you’re fighting gravity or that gravity would slow you down, which isn’t correct on a downward grade.

Gravity's effect on speed when moving downhill is the key idea. On a downgrade, gravity pulls the vehicle downhill along the slope, so the component of gravitational force acts in the direction of travel. This adds energy to the motion, converting potential energy into kinetic energy, which tends to increase speed if you don’t brake. In other words, you’re working with gravity, not against it, so speed rises as you descend. Of course, braking or engine braking can counter this and keep speed in check, but without braking the vehicle would accelerate. The other options imply you’re fighting gravity or that gravity would slow you down, which isn’t correct on a downward grade.