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प्रश्न
State the empirical laws of static and kinetic friction.
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उत्तर
The empirical laws of friction are:
- Friction is independent of the surface of contact.
- The coefficient of kinetic friction is less than the coefficient of static friction.
- The direction of frictional force is always opposite to the motion of one body over the other.
- Frictional force always acts on the object parallel to the surface on which the object is placed,
- The magnitude of frictional force between any two bodies in contact is directly proportional to the normal reaction between them.
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संबंधित प्रश्न
Explain various types of friction.
Suggest a few methods to reduce friction.
People often say “For every action, there is an equivalent opposite reaction”. Here they meant ‘action of a human’. Is it correct to apply Newton’s third law to human actions? What is mean by ‘action’ in Newton's third law? Give your arguments based on Newton’s laws.
A block of mass 20 kg is sliding on a surface is inclined at an angle of 45° with the horizontal. What will be the acceleration of the block if the coefficient of kinetic friction between the block and the surface is 0.7?
A block of mass m slides along a floor while a force of magnitude F is applied to it at an angle θ as shown in figure. The coefficient of kinetic friction is µK. Then, the block's acceleration 'a' is given by ______.
(g is acceleration due to gravity)
A 40 kg wooden crate is being pushed across a wooden floor with a force of 160 N. If µk = 0.3, the acceleration of the crate is ______ m/s2. (g = 10 m/s2}
A block of mass m = 1 kg moving on horizontal surface with speed u = 2 m/s enters a rough horizontal patch ranging from x = 0.10 m to x = 2.00 m. If the retarding force fr on the block in this range is inversely proportional to x over this range i.e.
fr = `"-k"/x` 0.10 < x < 2.00
= 0 for x < 0.10 and x > 2.00
If k = 0.5 J then the speed of this block as it crosses the patch is (use ℓn 20 = 3)
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The coefficient of static friction between a car's tires and a level road is 0.80. If the car is to be stopped in a maximum time of 3.0 s, its speed cannot exceed.
A body starts from rest on a long inclined plane of slope 45°. The coefficient of friction between the body and the plane varies as µ = 0.3 x, where x is distance travelled down the plane. The body will have maximum speed (for g = 10 m/s2) when x = ______.
