Question

Use your knowledge of friction to explain the following statements:

a) A car pulling a trailer uses a lot of petrol.
b) A nail file is made of rough material.
c) When you apply brakes as you are driving down a steep hill , the brakes become hot.
d) A fish can travel very quickly through water​

Answer 1

a) A car pulling a trailer uses a lot of petrol.

• The trailer creates drag as it moves through the air, resulting in more air resistance and friction. The engine has to work harder to overcome this additional friction, using more fuel.

b) A nail file is made of rough material.

• The roughness of a material increases the friction between it and another surface. Since a nail file works by creating friction with nails, it needs to be made of a rough material to provide enough grip.

c) When you apply brakes as you are driving down a steep hill , the brakes become hot.

• The brakes create friction with the disc or drum in the wheels to slow the car down. The friction generates heat, causing the brakes to heat up. The steeper the hill, the more force is needed from the brakes and the hotter they become.

d) A fish can travel very quickly through water​

• Water provides much greater friction than air, making it more difficult to move through. However, fish are specially adapted to reduce friction in water through their streamlined shape and fins. This allows them to travel relatively quickly with less resistance.

Answer 2

a) A car pulling a trailer uses a lot of petrol: When a car pulls a trailer, it experiences an increase in frictional forces. The car's engine needs to work harder to overcome the additional resistance caused by the friction between the tires and the road. The frictional force opposes the motion of the car and trailer, requiring more power from the engine. This increased power demand leads to higher fuel consumption, resulting in the car using a lot of petrol.

b) A nail file is made of rough material: A nail file is designed to shape and smooth the surface of nails. To achieve this, it is made of a material with a rough surface, often containing small abrasive particles. When the nail file comes into contact with the nail, the rough surface creates friction between the file and the nail. This friction helps to remove tiny layers of the nail, resulting in the filing and smoothing effect.

c) When you apply brakes as you are driving down a steep hill, the brakes become hot: When brakes are applied, they generate friction to slow down or stop the vehicle. When driving down a steep hill, the brakes are required to dissipate a large amount of kinetic energy quickly. This is accomplished by converting the kinetic energy into thermal energy through friction between the brake pads and the brake rotors or drums. The friction generates heat, causing the brakes to become hot. The steeper the hill or the longer the braking duration, the more heat is generated, potentially leading to overheating of the braking system.

d) A fish can travel very quickly through water: Fish are well-adapted to swimming in water due to various factors, including the role of friction. As a fish moves through water, the interaction between the fish's streamlined body and the water creates frictional forces. These frictional forces, combined with the fish's muscular movements, propel it forward. The streamlined shape of the fish reduces the resistance caused by friction, allowing it to move efficiently through water. Additionally, fish have evolved specialized fins and tails that provide thrust and maneuverability, further optimizing their movement through the water.