Force from engine power

Type power P [W] and speed v [m/s]. The calculator computes F = P/v: 10000 W at 20 m/s is 500 N. You must type 75 kW as 75000, or F comes out a thousand times too small. Zero m/s does not divide.

Power from force: P = F·v. Force from mass: F = m·a. Power from work: P = W/t.

Inputs

Result

Power P (W) and Speed v (m/s). The result shows up here.

How it works

P, v F F = P/v N ← W, m/s
From power and speed you get force. Inverse of P = F·v.

When you know power and speed, the force along v is the quotient: F = P / v. Ten thousand watts at 20 m/s give 500 N. That is the same relation as P = F·v, only the unknown is F. A newton times a meter per second folds back into a watt.

A nameplate often speaks kilowatts. 10 kW is 10000 W. If you type 10 at v = 20, you get 0.5 N, a hundred times too small for that problem. 75 kW at 25 m/s is 75000 / 25 = 3000 N. A bike at 400 W and 2 m/s is 200 N.

Speed must be in m/s. 72 km/h is 20 m/s. Typing 72 instead of 20 at 10000 W gives about 139 N instead of 500. Twice the v at the same P means half the F: at 40 m/s those same 10000 W are already 250 N.

This is the force needed to hold that power at that v, not F = m a from acceleration. When a car rolls at constant speed, this F balances drag. Acceleration lives on F = m·a. Average power from energy and time lives on P = W/t.

P and v must be positive. The model is “something pulls and it moves.” The result is in newtons. With that F you can go to work W = F·s, or return to P = F·v and check that 500 × 20 is 10000 W again.

Type P in watts and v in m/s, then Calculate. 10000 and 20 should come back as 500 N. A comma in 2.5 works when v is a fraction.

How to use

  1. Type power in watts. 10 kW is 10000. 75 kW is 75000. A 400 W bike stays 400.
  2. Type v in m/s. Convert 72 km/h to 20. Two meters per second is 2.
  3. Click Calculate. 10000 W and 20 m/s give 500 N. 75000 and 25 give 3000 N.
  4. 400 W and 2 m/s give 200 N. The same 10000 W at 40 m/s give 250 N.
  5. When you know F and v and want P, open P = F·v. Here the unknown is F.

Formula

F = P / v

P > 0, v > 0. Unit of F: newton.

F, P, and v in F = P/v

Force from power and speed, not P = F·v. 10000 W at 20 m/s is 500 N. Type 75 kW as 75000 W, not as 75.

F
Force along the motion [N]. 10000 / 20 = 500 N. Pair of P = F·v on the next card.
P
Power [W]. 10000 W or 75000 W. Multiply kilowatts by 1000 before you type.
v
Speed [m/s]. 20 m/s, not 72 km/h. v must be positive.

Real-life examples

Example 1

P = 10000 W, v = 20 m/s -> F = 500 N.

Example 2

P = 75000 W, v = 25 m/s -> F = 3000 N.

Example 3

P = 400 W, v = 2 m/s -> F = 200 N.

Example 4

P = 50 W, v = 1 m/s -> F = 50 N.

Example 5

P = 375000 W, v = 25 m/s -> F = 15000 N.

Example 6

P = 4000 W, v = 5 m/s -> F = 800 N.

Example 7

P = 1500 W, v = 3 m/s -> F = 500 N.

Example 8

P = 100000 W, v = 10 m/s -> F = 10000 N.

Ways to use this calculator

  • From 10 kW and 20 m/s you check 500 N, remembering to type 10000, not 10.
  • From a 75 kW plate and 90 km/h (25 m/s) you compute 3000 N on a straight.

Related calculators

Force F = m·a
Force from mass and acceleration, no engine power.
Power P = W/t
Power from energy and time, no force along the path.
Power from force and velocity P = F·v
Engine power when force and speed point the same way.
Engine work calculator W = P·t
Work from power held steady for the time you typed.
Time from work and power t = W/P
How long known work takes at a steady power.
Work W = F·s
Force from power and speed, then work along distance s.

All physics calculators

Frequently asked questions

How much F at 10000 W and 20 m/s?

Force is 500 N. That is 10000 / 20. At 40 m/s the same 10000 W give 250 N: twice the v, half the F.

How much at 75 kW and 25 m/s?

First 75000 W. 75000 / 25 = 3000 N. Typed 75 gives 3 N, a factor-thousand slip, because the field wants watts.

How much at 400 W and 2 m/s?

Force is 200 N. That is bike scale on a short climb, not a car at 75 kW.

Do I type 10 kW as 10?

No. The field wants watts. 10 kW = 10000 W. A ten at 20 m/s is 0.5 N, not 500.

Can I type 72 km/h as 72?

No. 72 km/h = 20 m/s. 10000 / 72 would give about 139 N instead of 500 N at the same power.

How is this different from P = F·v?

Same relation, different unknown. There you solve for power. Here you pull force F [N] from P and v.

How is this different from F = m·a?

There mass and acceleration. Here power and speed. The newton is shared, the fields differ.

Where is average power from work?

On P = W/t. Here instantaneous F = P/v at a given v, with no work W in the form.

How do I get work from this F?

On W = F·s. 500 N over 100 m is 50000 J. Here F is the result, not a path.

Does a comma in 2.5 work?

Yes. 2.5 and 2,5 are the same v [m/s]. 10000 / 2.5 = 4000 N.

Knowledge sources

The formula is the school one. Units follow SI; NIST SP 330 and BIPM define the measures, not your result.

Page updated in 2026.