Friction (part-3)

FRICTION

Q.6. What is spring balance? How does it work?
Ans. Spring balance is a device used for measuring the force acting on an object. It consists of a coiled spring which gets stretched when a force is applied to it. Stretching of the spring is measured by a pointer moving on a graduated scale. The reading on the scale gives the magnitude of the force.
                                                  


Q.7. What are static, sliding and rolling friction?
Ans. The force required to overcome friction at the instant an object starts moving from rest is a measure of static friction.
The force required to keep the object moving with the same speed is a measure of sliding friction.
When a surface rolls over another, the friction which slows down the motion of rolling object is called rolling friction.

                             Static friction > sliding friction > rolling friction

Q.8. The sliding friction is slightly smaller than the static friction. Give reason.
Ans. In case of static friction, irregularities of the surfaces have enough time to get properly interlocked because objects remain at rest for a long time.

In case of sliding friction, the objects remain in motion with respect to each other, so their irregularities do not have enough time to get properly interlocked as it was interlocked in static friction.
More interlocking means more friction and less interlocking means less friction so static friction is more than sliding friction. 
                                 




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