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Physics Part I

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Class 10 Class 12
Two trains are moving in opposite directions on parallel tracks, one with a velocity twice that of the other. If the total length of two trains is 480 ft and they take 3 seconds to cross each other, find their individual velocities. 

Let the two trains A and B be moving in the opposite directions with velocities u and 2u respectively.

Relative velocity, V = u + 2u = 3u 

Total distance moved = total length of two trains.

i.e. S = 480 ft.

Time taken by trains to cross each other, t = 3 sec

Now, S     = Vt

rightwards double arrow    480 = 3u x 3

rightwards double arrow      2u = 106.66 ft/s 

rightwards double arrow        u = 53.33ft/s 


What are the basic characteristics that a quantity must possess so that it may be a vector quantity?

A quantity must possess the direction and must follow the vector axioms. Any quantity that follows the vector axioms are classified as vectors. 


What is a vector quantity?

A physical quantity that requires direction along with magnitude, for its complete specification is called a vector quantity.

What is a scalar quantity?

A physical quantity that requires only magnitude for its complete specification is called a scalar quantity.

Give three examples of vector quantities.

Force, impulse and momentum.

Give three examples of scalar quantities.

Mass, temperature and energy