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Class 10 Class 12
A car starts from rest and accelerates uniformly with 2 m/s2. At t = 5s a stone is dropped out of the window 15 m high of the car. What is velocity and acceleration of stone at t = 5·5 s? ( g = 10m/s2).

Given,

Car starts from rest. That is,

Initial velocity = 0 m/s
Uniform acceleration of the car = 2 m/s2
Velocity of car at t = 5s =  10 m/s

When stone is dropped, the velocity of car and hence velocity of stone is 10 m/s in horizontal direction.

Since at 5s the stone loses the contact from car, therefore, the stone will move uniformly in horizontal direction and accelerate in vertically downward direction due to gravity.

At t = 5·5s or 0·5 s after the stone is dropped, the X and Y component of velocity are

So, magnitude of velocity is given by,

Acceleration of the stone at t=5.5 sec is the same as acceleration due to gravity.

That is, acceleration = 10 m/s2

And,

Angle of inclination with the horizontal,  =

i.e.,

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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.

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Give three examples of vector quantities.

Force, impulse and momentum.
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What is a scalar quantity?

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

A physical quantity that requires direction along with magnitude, for its complete specification is called a vector quantity.
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Give three examples of scalar quantities.

Mass, temperature and energy
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