Vehicle resistance calculations: A truck weighs 63 500 N and has a coefficient of rolling resistance of 0.018. What is the rolling resistance force acting on the truck (in newtons)?

Introduction / Context:

Rolling resistance is a fundamental road-load component that opposes vehicle motion. It arises from tire deformation, hysteresis, and road interaction, and it is typically modeled as proportional to the vehicle's normal load via a coefficient of rolling resistance. This problem applies the basic formula to compute the rolling resistance force for a specified truck weight and coefficient—an essential step in tractive-effort and fuel-economy analyses.

Given Data / Assumptions:

• Vehicle weight W = 63 500 N (acts as normal force on level ground, neglecting aerodynamic lift/squat).
• Coefficient of rolling resistance f_r = 0.018 (dimensionless).
• Level road; speed effects on f_r neglected.

Concept / Approach:

The rolling resistance force on level ground is modeled as F_rr = f_r × W. This linear relation is widely used in first-order vehicle dynamics. Units remain in newtons because f_r is dimensionless and W is in newtons.

Step-by-Step Solution:

Verification / Alternative check:

Estimate: 0.02 × 63 500 = 1 270 N; since 0.018 is 10% less than 0.02, reduce by ≈127 N → ≈1 143 N. This mental-math check confirms the exact calculation.

Why Other Options Are Wrong:

• 114.3 N and 11.43 N / 1.143 N: each is off by one or more powers of ten—a common decimal-placement error.
• 1.143 kN: although numerically equivalent to 1 143 N, the option set expects units in newtons; selecting kN would be mismatched unless explicitly allowed.

Common Pitfalls:

• Mistaking vehicle mass (kg) for weight (N) and introducing an extra g factor.
• Applying grade resistance or aerodynamic drag to a pure rolling-resistance question.

Final Answer:

1143 N