I think the correct answer is light energy. It is light energy that is transformed into chemical energy by plants by the process called photosynthesis. In this process, plants<span> take in water, carbon dioxide, and sunlight and </span>turn<span> them </span>into<span> glucose and oxygen.</span>
The hint is "constant speed".
If there is a net force on an object, what occurs to that object? F net = m*a.... It accelerates!
So, if the desk is going at a CONSTANT speed, what does that tell you about the acceleration? There is a change in speed.
Fnet = m*a Since a = 0 Fnet = 0
Fnet = sum of the force... reflect the direction of F as the positive direction. Sum of the forces in the direction of F = 0 0 = F - friction F = friction
So, if F = 800 N, then friction = 800 N in the opposite direction.
