In the following statement in which case work is to be done
A man is carrying a weight and stands still
A crow is sitting on a cow
A man climbs a stair case with the weight
A woman sitting on a chair
In which of the following cases is friction a disadvantage to us ?
Running
Breaking
Writing with pencil
Parts of a machine rubbing with each other
___________ are used to reduce friction in rotating parts such as wheels rotating about a fixed shaft.
Grease
Ball bearings
Metal rods
None of these
When a body has an excess of one kind of charge, it is said to be charged. It then applies a force, called ___________ , on other charged bodies near it.
Gravitational force
Elastic force
Electrostatic force
