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Find force and power for moving a load

Horizontal movement and lifting need different forces. Separate the sources of resistance before calculating force and power.

Horizontal sliding load with rightward drive force and speed, leftward friction, weight and normal reaction; wheel radius inset.mFμNv, amgNrT = FrPinput = Fv/ηDrive wheel
Side view of a horizontal sliding model. Red driving force F acts right, blue friction μN acts left. Right is positive for velocity v and acceleration a.

What you will understand

  • Separate friction, slope and acceleration
  • Distinguish breakaway/running and force/power
  • Keep wheel and motor-shaft values distinct

Blue: defined conditions · Red: calculated quantities. Diagrams are schematic.

  • m, μ, a, v: mass, friction, acceleration and velocity
  • F: running drive force, P: drive input power
  • r: drive-wheel radius, T=Fr: torque on that shaft

The examples below are illustrative. Each example button loads its fixed values, units and mode. Ordinary calculator links do not load an example.

Define resistance and travel direction

This model moves a sliding load forward using force parallel to a straight track. Enter zero slope for level, positive uphill and negative downhill. It does not directly represent rolling resistance or an entire belt conveyor.

  • Moving mass and actual contact/resistance conditions
  • Distinguish 5% grade from 5°
  • Separate kinetic μk and static μs for breakaway

Separate starting, running and power

The breakaway result is a static-friction boundary without acceleration. Running force uses kinetic friction and ma. Power depends on speed; zero power while stopped does not mean zero holding force.

For practical review

Accelerating from rest also requires inertial force beyond breakaway resistance. Rotating inertia, belt flex/tension, bearings and aerodynamic drag are excluded. When using measured resistance, avoid counting the same losses twice.

N=mg cosθ, F=ma+mg sinθ+μkN / Fstart=max(0,mg sinθ+μsN) / for F≥0, Pinput=Fv/η

Read force, power and torque together

Torque Fr refers to the drive wheel or drum shaft. It is distinct from motor-shaft torque through a gearbox.

Example: move 20 kg on a level slide

Inputs

  • m=20 kg, θ=0°, μk=0.1, μs=0.15
  • a=0.5 m/s², v=0.2 m/s, η=80%
  • Drive-wheel radius r=50 mm (coefficients illustrative)

Results

  • Running F=29.6133 N; breakaway boundary 29.4200 N
  • Required input power P≈7.403 W
  • Drive-wheel torque T≈1.481 N·m

Do not select a motor from 7.403 W alone. Check starting, acceleration, cruising and stopping torque/speed, duty, and gearbox/drum/transmission ratings.

Load the fixed values, units and mode for this illustration. Then edit them for your conditions.

Negative force indicates a braking demand

Downhill travel or deceleration can give negative F. This does not command reverse travel: the forward-moving load requires an opposing force.

  • Stopping distance, holding and power-loss behavior
  • Regeneration, resistor/brake capacity and cycle frequency

For F<0, mechanical braking power to absorb is Pbrake=−Fv

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Reference information and illustrative calculations. This content does not guarantee suitability or safety of a design. Confirm the actual materials, component specifications and operating conditions.