What is the coefficient of static friction between a load of mass 2kg and a horizontal surface, if the limiting frictional force is 10N? (g = 10 $ms^{-2}$)

Analyze the question: We need the coefficient of static friction (μ) given the mass, the limiting friction, and g.

Concept: Limiting friction is the maximum static friction before the object starts to slide:

F = μR

On a horizontal surface, the normal reaction R equals the weight of the load:

R = mg

So μ = F / (mg)

Solution:

• Mass, m = 2 kg
• g = 10 m/s²
• Normal reaction, R = mg = 2 × 10 = 20 N
• Limiting friction, F = 10 N

μ = F / R = 10 / 20 = 0.5

Answer: B. 0.5

Tip: The coefficient of friction has no units because it is a ratio of two forces. On a flat surface, always find R = mg first, then use μ = F/R. Also, if you get μ greater than 1, double-check your working, since most exam problems give values between 0 and 1. That helps you rule out options like C, D, and E here.