Determine the magnitude (the value or number) of the force in the direction of motion. If the force is completely in the direction of motion, this number is simply the value of the force. If the force is at an angle to the direction of motion, use trigonometry to calculate the component that is in the same direction as the motion. For example, if a car is traveling along the x-axis, and the force is 50 N at an angle of 30 degrees above the x-axis, then use 50cos(30) N for the force.
Multiply the force by the speed to find power.
Label your answer with the appropriate units. The international unit for power is the watt (W), but other units include horsepower (hp) and foot-pounds per second (lb/s). The units of the force and speed will determine the units of power.
Determine the force in the direction of motion.
Divide power by the force.
Label your answer in meters per second (m/s), miles per hour (mph), kilometers per hour (km/h) or other unit based on the dimensions of power and force.