A car's engine applies a 500 N driving force at a steady 20 m/s on a level highway.
What power does the engine deliver?
Start with the car's numbers: F = 500 N, v = 20 m/s.
500 × 20 = 10000. The engine delivers 10000 W.
That move is the equation you have: P = Fv.
Big powers read naturally in kilowatts: one kilowatt (1 kW) is 1000 W, so 10000 W is 10 kW.
Finding a power from force and speed is a routine, and the same three steps work every time.
Step 1: write down the values, and mark the unknown.
Step 2: write down the equation.
Step 3: substitute in the values, and calculate. The result line carries its unit: watts, or kilowatts when the number runs large.
A car's engine applies a 500 N driving force at a steady 20 m/s. Calculate the power delivered.
Write down the values in the question:
F = 500 N, v = 20 m/s; P = ?
Write down the equation:
P = Fv
Substitute in the values, and calculate:
P = 500 × 20 = 10000
The engine delivers 10000 W, which reads naturally as 10 kW.
A winch cable applies a constant 250 N force to a loaded pallet moving at a steady 6 m/s, parallel to the motion. Enter the power delivered, in watts.
An electric scooter's motor applies a constant 300 N driving force at a steady 7 m/s. Calculate the power delivered.
Write down the values in the question:
F = 300 N, v = 7 m/s; P = ?
Write down the equation:
P = Fv
Substitute in the values, and calculate:
P = 300 × 7 = 2100
The motor delivers 2100 W.
A conveyor motor applies a constant 80 N force to a parcel stream moving at a steady 4.5 m/s. Enter the power delivered, in watts.
A tractor applies a constant 1200 N force to a loaded wagon it tows at a steady 15 m/s. Enter the power delivered, in watts.
A speedboat's propeller applies a constant 750 N driving force as the boat holds a steady 16 m/s. Enter the power delivered, in watts.
A cyclist applies a constant 45 N driving force at a steady 9 m/s on a flat road. Enter the power delivered, in watts.
A freight locomotive applies a constant 24000 N driving force at a steady 5 m/s up a long grade. Enter the power delivered, in kilowatts.