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10Oil and grease are used in machines to increase friction.
Friction reduces the efficiency of machines.
Friction is more on smooth surfaces than rough surfaces.
Lubricants make surfaces smoother.
Rolling friction is less than sliding friction.
Ball bearings increase friction in machines.
Water reduces friction between surfaces.
Streamlined shape increases air resistance.
Aeroplanes are given streamlined shape to reduce friction.
Friction is always useful in machines.
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Why is oil used in door hinges?
Which friction is less?
What is used in machines to reduce friction?
Which device is used to measure force?
Ball bearings are used because they:
Which shape reduces air resistance?
Friction between sliding surfaces can be reduced by:
Which object is streamlined?
Friction converts kinetic energy into:
Which friction is used in ball bearings?
Friction is reduced by using ______ and grease.
Friction between rough surfaces is ______ than smooth surfaces.
Ball bearings reduce ______ friction.
Rolling friction is ______ than sliding friction.
Lubricants make moving surfaces ______.
Spring balance is used to measure ______.
Aeroplanes and ships have ______ shape.
Friction converts kinetic energy into ______ energy.
Ball bearings contain small ______ balls.
Narrow front shape reduces friction with ______ or water.