Explain why sliding friction is less than static friction.
Solution and Explanation
When the objects are at rest, the interlocking of irregularities in the two surfaces of the objects is higher than that of when objects are moving. When objects are moving, there is less interaction between their surfaces. That's why sliding friction is less than static friction.
Top CBSE Class VIII Science Questions
Select the correct word from the following list and fill in the blanks.
float, water, crop, nutrients, preparation- The same kind of plants grown and cultivated on a large scale at a place is called ____.
- The first step before growing crops is ____ of the soil.
- Damaged seeds would ____ on top of water.
- For growing a crop, sufficient sunlight and ____ and ____ from the soil are essential.
- List conditions under which combustion can take place.
- Match items in column A with those in column B.
A B (i) Kharif crops (a) Food for cattle (ii) Rabi crops (b) Urea and super phosphate (iii) Chemical fertilizers (c) Animal excreta, cow dung urine and plant waste (iv) Organic manure (d) Wheat, gram, pea (e) Paddy and maize - Fill in the blanks:
- Burning of wood and coal causes ___ of air.
- A liquid fuel, used in homes is ___.
- Fuel must be heated to its ___ ___ before it starts burning.
- Fire produced by oil cannot be controlled by ___.
- Explain how the use of CNG in automobiles has reduced pollution in our cities.
Top CBSE Class VIII Force of Friction Questions
- Fill in the blanks.
- Friction opposes the ___ between the surfaces in contact with each other.
- Friction depends on the ___ of surfaces.
- Friction produces ___.
- Sprinkling of powder on the carrom board ___ friction.
- Sliding friction is ___ than the static friction.
- Alida runs her toy car on dry marble floor, wet marble floor, newspaper and towel spread on the floor. The force of friction acting on the car on different surfaces in increasing order will be
- Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.
- You spill a bucket of soapy water on a marble floor accidently. Would it make it easier or more difficult for you to walk on the floor? Why
- Explain why sportsmen use shoes with spikes.
Top CBSE Class VIII Questions
- Solve the following equation and check your result: \(3x = 2x + 18\)
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Concepts Used:
Friction
Friction is defined as the resistance offered by the surfaces that are in contact when they move past each other.
Types of Friction
There are four categories of Friction- static friction, sliding friction, rolling friction, and fluid friction.
Sliding Friction
In Sliding Friction, the weight of the sliding object calculates the amount of sliding friction present between the two objects. The sliding friction is supposed to be greater as the pressure exerted by the heavy object on the surface it slides over is comparably more.
Rolling Friction
Friction between a circular object and the surface is called as Rolling Friction. It is required to overcome sliding friction is more than the force required to overcome the rolling friction.
Static Friction
Friction that keeps an object at rest without initiating any relative motion between the body and the surface is termed as Static Friction. For example, a parked car resting on the hill, a hanging towel on the rack. The maximum force of static friction is directly proportional to the normal force.
Fluid Friction
Fluid Friction is the kind of friction that is exerted by the fluid on the object that is moving through a fluid.