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Motion in Straight Line

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Physics Part I

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
A player throws a ball upwards with an initial speed of 29.4 m s-1.

To what height does the ball rise and after how long does the ball return to the player’s hands ?
(Take g = 9.8 m s-2and neglect air resistance).

Initial velocity of the ball, u = 29.4 m/s 

At maximum height, the velocity of the ball becomes zero.

Final velocity of the ball, v = 0 

Acceleration, a = – g = – 9.8 m/s2  

Using third equation of motion, 

Height to which the ball rises is given by, 

straight v squared space minus space straight u squared space equals space 2 gs

straight s space equals space fraction numerator left parenthesis straight v squared minus straight u squared right parenthesis over denominator 2 straight g end fraction space

space space equals fraction numerator space left square bracket left parenthesis 0 right parenthesis squared space minus space left parenthesis 29.4 right parenthesis squared right square bracket space over denominator 2 cross times left parenthesis negative 9.8 right parenthesis end fraction space space equals 44.1 space straight m
Also comma space

Time space of space ascent space equals space Time space of space desent space

So comma space total space time space taken space by space the space ball space to space return space to space the space
p layer apostrophe straight s space hand space is comma

straight t space equals space 3 space plus space 3 space equals space 6 space sec


What is rest?

When an object does not change its position with time, with respect to it's surroundings. In such a case the object is said to be at rest. 

Can a body be always at rest in some frame?

Yes, a body is always at rest in a frame which is fixed with the body itself. 

What is the most essential thing to study the motion of a body?

The most essential thing to study the motion is reference frame. Rest and motion are relative terms. It means that an object in one situation can be in rest but in another situation, the same object will be in motion. 

Is absolute rest or absolute motion possible?

Absolute rest and absolute motion is not possible because there is no point in the universe which is at rest and can be taken as point of reference. The planet Earth is in continuous motion. 

What is motion?

When an object changes it's position with time, with respect to it's surroundings, the object is said to be in motion.