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Motion In Straight Line

Question
CBSEENPH11017092
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A ball is thrown vertically upwards from the top of a tower 80m high and reach the ground in 6 seconds. Find the velocity with which the ball is thrown?

Solution
Consider, ground as reference point and vertically upward direction as positive. 
Height of the tower, h = 80 m 
Acceleration due to gravity, a = -10 m/s2 
Time taken for the ball to reach the ground = 6 seconds
Here, 
straight x subscript 0 space equals space straight h space equals space 80 space straight m space space space space space space space straight a space equals space straight g space equals space minus 10 space straight m divided by straight s squared straight t space equals space 6 space sec space space space space space space space space space space space space space space space space space space straight x space equals space 0 space
Let  be the initial velocity of the ball. 
So, usign equation of motion, we have
space space space space space space space space straight x space equals space straight x subscript 0 space plus space ut space plus space 1 half at squared space therefore space space space space space 0 space equals space 80 space plus space straight u cross times 6 space minus 1 half cross times 9.8 cross times left parenthesis 6 right parenthesis squared space space space space space space space space space space 0 space equals space 80 space plus space 6 straight u space minus 1 half cross times 9.8 space cross times 36 space space space space space space space space space space 0 space equals space 80 space plus space 6 straight u space minus 176.4 space space space space space space space space space space space straight u space equals space 16.07 space straight m divided by straight s

So, u = 16.07 m/s is the velocity with which the ball is thrown. 
 
 

Some More Questions From Motion in Straight Line Chapter

Is absolute rest or absolute motion possible?

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

Can a body be always at rest in some frame?

Can a body be in motion in the frame associated with the body itself?

When an object in motion can be considered as particle or point object?

Can you think of physical phenomena involving the moon in which moon cannot be treated as particle?

A train is crossing the bridge. Can it be taken as a particle?

Can a train be taken a particle? Give an example in support of your answer.

 A particle is moving along curved line in space. Is the motion one dimensional?

State which of the following are examples of one, two or three dimensional motion: 

(a) A kite flying in the sky.

(b) The earth revolving around the sun. 

(c) A train moving along the equator of the earth in clockwise direction. 

(d) Accelerated motion of a particle in a straight line.

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