Question

A block of mass 10 kg is placed on a long trolley. The coefficient of friction between the block and trolley is 0.2. The trolley accelerates from rest with 0.5 m/s2 for 20 s. then what is the friction force? (1) 20 N (2) 100 N (3) 5 N (4) 10 N​

Answer 1

Answer:

• Friction is a constant force

• It always opposes the relative motion between two objects.

• Two types of friction:

1. Static friction
2. Kinetic friction

Solution:

•Coefficient of static friction (μ) = 0.2

• mass of block (m) = 10 kg

• Acceleration (a) = 0.5 m/s²

• Time (t) = 20 s

Frictional force:

=> F = μN

=> F = μmg

=> F = 0.2 × 10 × 10

=> F = 0.2 × 100

=> F = 20 N

Hence,the Option (1) 20 N is the correct answer.

Answer 2

Given:

mass of block (m) = 10 kg

Acceleration (a) = 0.5 m/s²

Time (t) = 20 s

Coefficient of static friction (μ) = 0.2

 Find frictional force=?

Formula of friction force is:

F = μN

F = μmg

F = 0.2 × 10 × 10  

F = 0.2 × 100

F = 20 N

The correct option is "1"

Hence friction force is 20 N