Friction — Set 4
Physics · घर्षण · Questions 31–40 of 60
Which of the following is a way to reduce friction in a door hinge?
Correct Answer: A. Applying oil
Applying oil to a door hinge reduces friction and stops the squeaking sound. The oil coats the moving parts and prevents them from grinding against each other. This is a simple form of liquid lubrication.
The rolling friction of a wheel is generally _____ than its sliding friction.?
Correct Answer: A. Lower
Rolling friction is much lower than sliding friction because the contact area is smaller and the surfaces do not rub. This is why the invention of the wheel was so revolutionary for transportation. Moving a heavy load on rollers is always easier than dragging it.
What is the role of friction when we are braking a car?
Correct Answer: D. It stops the car
The correct answer is 'It stops the car'. Braking works by creating friction between the brake pads and the wheels to stop the car. This friction converts the car's kinetic energy into heat energy, causing the vehicle to slow down. Modern braking systems are designed to maximize this stopping force safely.
Which of these materials would likely have the lowest coefficient of friction when sliding on steel?
Correct Answer: C. Teflon
Teflon is famous for having an extremely low coefficient of friction against most materials. It is used in non-stick cookware to prevent food from sticking to the pan. This property makes it very useful in industrial applications where low friction is required.
The force of friction between two surfaces depends on _____.?
Correct Answer: B. Nature of the materials
Friction depends on the nature of the materials and how they interact at a microscopic level. For example, rubber on concrete has much more friction than ice on steel. The chemical bonding and physical structure of the materials determine the friction.
Why is it easier to pull a suitcase with wheels than one without?
Correct Answer: C. Rolling friction is less than sliding friction
Wheels replace sliding friction with rolling friction, which is much weaker. This makes it possible to move heavy luggage with very little effort. Almost all modern luggage is designed with wheels for this convenience.
What happens to the temperature of two stones when they are rubbed against each other?
Correct Answer: B. It increases
The temperature increases because friction converts the work done in rubbing into heat. This method was traditionally used by early humans to start fires. The friction between the stones provides the necessary activation energy for combustion.
Friction between the clouds and the air can lead to the build-up of _____.?
Correct Answer: D. Static electricity
The friction between air and water droplets in clouds can generate large amounts of static electricity. This accumulation of charge eventually discharges as lightning. This is a natural example of friction causing electrical phenomena.
Which of the following describes 'limiting friction'?
Correct Answer: C. Maximum static friction
Limiting friction is the maximum value of static friction that occurs just before an object starts moving. It represents the 'breaking point' of the frictional bond between two surfaces. This value is used to calculate the coefficient of static friction.
Friction can be reduced by using which of the following in machines?
Correct Answer: D. Graphite powder
Graphite powder is a solid lubricant used in situations where oil might attract dust or be messy. It has a layered structure that allows the layers to slide over each other easily. It is commonly used in locks to ensure smooth operation.