Why do we use ball-bearings?

Why do we see water droplets collected on the outer surface of a glass container?

Why do we prefer to use a wrench with a long arm?

Why do we prefer mercury in a barometer?

Why do we require artificial sweetening agents?

Why do we feel cooler under the fan?

Why do we place handles at maximum possible distance from the hinges in a door?

Two identical ball bearings in contact with each other and resting on a frictionless table are hit head-on by another ball bearing of the same mass moving initially with a speed VL If the collision is elastic, which of the following figure is a possible result after collision?

Why do you have to use paper or kerosene oil to start fire in wood or coal?

When do we call a body rigid?