I) Friction is a force that opposes the relative motion or tendency of motion between two surfaces in contact.

a)

i) Friction is a force that opposes the relative motion or tendency of motion between two surfaces in contact.

ii)

• ($\alpha$) Desirable situations:
  • Walking or running on the ground.
  • Braking a vehicle.
• ($\beta$) Undesirable situations:
  • Wear and tear in machine parts.
  • Energy loss in moving engine components.

b)

i) A body undergoes simple harmonic motion if:

• Its acceleration is directly proportional to its displacement from the equilibrium position.
• Its acceleration is always directed towards the equilibrium position.

ii)

Step 1: Calculate the period of the simple pendulum ($T_1