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94/3334–6FE Reference Handbook 10.4 · Dynamics · Power
1. Constant Acceleration2. Newton’s Second Law3. Work–Energy Principle4. No-Time Acceleration Equation5. Position–Time Equation6. Impulse–Momentum Principle7. Translational Kinetic Energy8. Normal (Centripetal) Acceleration9. Level-Ground Projectile Range10. Power11. Angular Form of Newton’s Second Law12. Relative Velocity13. Coefficient of Restitution14. Elastic Spring Energy15. Rigid-Body Rotation: Tangential and Normal Accel.16. Mass Moment of Inertia17. Conservation of Mechanical Energy18. Angular Impulse–Momentum19. Rolling Without Slip20. Polar / Path Normal–Tangential Acceleration21. Instantaneous Center of Zero Velocity22. Work of a Variable Force

Handbook formula

Power

Power is the time rate of work. For a force aligned with velocity, P = Fv. Average power is ΔW/Δt. The SI unit is the watt (J/s); 1 hp ≈ 746 W.

(W)
Power
(N)
Force
(m/s)
Velocity
(J)
Work

Step-by-step solved example

A constant 400 N traction force at 15 m/s (aligned). Power?

TL
Power P = Tω for a rotating shaft.

  1. 1. Dot product

    P = Fv = 400 × 15 = 6000 W.

  2. 2. kW

    6000 W = 6.00 kW.

Answer: 6.00 kW

10 practice questions

0/10 correct

1.F = 200 N, v = 10 m/s aligned. P =

2.5 kW delivered for 4 s. Energy =

3.Power is

4.SI unit of power is

5.Towing 800 N at 5 m/s. P =

6.If F is perpendicular to v, instantaneous P is

7.Instantaneous mechanical power of a force is

8.50 kW at 25 m/s. Traction force =

9.1 mechanical horsepower is about

10.Average power if W = 1200 J in 3 s is