Physics
Physics
Problem
A student is investigating the idea of power while pushing a laboratory trolley along a smooth floor. (i) State what is meant by the term power and write its SI unit. (ii) While the trolley moves with uniform velocity, the student claims that the rate at which she does work depends on both the force she applies and the speed of the trolley. Explain this statement qualitatively without using any numerical calculation. (iii) The same trolley-pushing arrangement is now operated by a motor that works at a constant power. If the speed of the trolley is doubled, describe and justify what happens to the magnitude of the horizontal force that the motor can exert on the trolley.Intuitive explanation
Power is the rate at which energy is transferred or work is done—how fast you're expending effort over time. The key insight for part (ii) is that work done equals force times distance, and since the trolley covers more distance per second at higher speeds, the same force does more work each second. For part (iii), remember that power is the product of force and velocity; if power stays constant but velocity doubles, the force must adjust inversely to keep their product unchanged.
Intuitive explanation
Power is the rate at which energy is transferred or work is done—how fast you're expending effort over time. The key insight for part (ii) is that work done equals force times distance, and since the trolley covers more distance per second at higher speeds, the same force does more work each second. For part (iii), remember that power is the product of force and velocity; if power stays constant but velocity doubles, the force must adjust inversely to keep their product unchanged.