To calculate the friction force acting on a towed mobile scissor lift as it moves, we generally consider rolling resistance (rather than sliding friction) since such lifts typically move on wheels.
Step-by-step Process:
1. Determine the Normal Force (Weight)
First, calculate the total weight of the scissor lift:
m: mass of the scissor lift (in kg)
g: acceleration due to gravity (approx. 9.81 m/s²)
If the lift is on a flat surface, the normal force is equal to the total weight.
2. Rolling Resistance Formula
The friction (resistance) force FrF_r due to rolling is:
Fr: rolling resistance force (in newtons)
Cr: coefficient of rolling resistance (dimensionless, typically 0.002–0.02 for rubber tires on concrete)
Example: For a 1500 kg lift with rubber tires on concrete:
Cr≈0.01C_r \approx 0.01, so:
3. Consider Inclines (if any)
If the lift is on a slope:
Add this to the rolling resistance if you're calculating the total force needed to tow uphill.
4. Add Wind or Drag (if moving fast)
If towed at significant speeds (e.g., behind a truck), include aerodynamic drag:
Where:
ρ: air density (≈ 1.225 kg/m³)
Cd: drag coefficient (~1.0–1.3 for blunt vehicles)
A: frontal area (m²)
v: velocity (m/s)
This is optional unless you're doing high-speed analysis.
Summary Formula (Flat Surface):
