Surface tension aids in capillary action, helping water to rise through the narrow xylem vessels from the roots to the leaves against gravity.
Which has greater viscosity, oil or honey? Why?
Honey has greater viscosity than oil because its internal friction between its layers is higher, making it flow more slowly.
Answer briefly.
 Define friction. Give two examples of the utility of friction in day to day life.
Friction is the force that opposes the relative motion or tendency of such motion of two surfaces in contact. It acts in the opposite direction of the moving object.
Examples:
Walking: Friction between our shoes and the ground allows us to walk without slipping.
Writing: Friction between the pen and paper allows us to write.
Mention any three ways of minimising friction.
Using lubricants: Applying substances like oil or grease between moving parts reduces friction.
Using ball bearings: Ball bearings convert sliding friction into rolling friction, which is significantly lower.
Streamlining: Designing objects like cars and airplanes with smooth, streamlined shapes reduces air resistance (a type of friction).
 State Pascal’s law and mention its applications.
Pascal’s Law: Pascal’s law states that the pressure applied to any point of a confined fluid at rest is transmitted undiminished in all directions throughout the fluid.
Applications:
Hydraulic lift: Used in car service stations to lift vehicles.
Hydraulic brakes: Used in vehicles to provide braking force.
Hydraulic press: Used to compress materials like cotton or cloth bundles.
 Why is a ball bearing used in a cycle hub?
A ball bearing is used in a cycle hub to reduce friction between the moving parts of the wheel and the axle. The ball bearings allow the wheel to rotate smoothly with minimal resistance, enhancing the efficiency and longevity of the cycle.
Answer in detail.
 Friction is a necessary evil – Explain.
Friction is called a necessary evil because it has both beneficial and detrimental effects.
Beneficial Effects:
Walking: We can walk without slipping due to the friction between our shoes and the ground.
Driving: Cars can move and stop safely because of the friction between tires and the road.
Holding Objects: We can hold and grip objects securely due to friction.
Detrimental Effects:
Wear and Tear: Friction causes wear and tear on moving parts of machines, leading to maintenance costs.
Energy Loss: A significant amount of energy is lost as heat due to friction in machines, reducing efficiency.
Noise and Heat: Friction generates unwanted noise and heat, which can be problematic in mechanical systems.
Give the different types of friction and explain each with an example.
Types of Friction:
Static Friction: The friction that acts on objects when they are at rest relative to each other. It must be overcome to start moving an object.
Example: Pushing a heavy box on the floor. The box does not move until the applied force exceeds the static friction.
Kinetic Friction: The friction that acts on objects when they are in motion relative to each other. It can be further divided into sliding and rolling friction.
Sliding Friction: Occurs when an object slides over another surface.
Example: Sliding a book across a table.
Rolling Friction: Occurs when an object rolls over a surface.
Example: Rolling a soccer ball on the ground. Rolling friction is usually less than sliding friction.
Explain how friction can be minimised.
Minimizing Friction:
Lubrication: Applying lubricants like oil or grease reduces the contact between surfaces, thus minimizing friction.
Ball Bearings: Using ball bearings reduces sliding friction by converting it to rolling friction, which is significantly lower.
Streamlining: Designing objects with smooth, streamlined shapes reduces air resistance, a form of friction.
Polishing Surfaces: Making surfaces smoother reduces friction by minimizing the microscopic irregularities.
