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Motion In Straight Line

Question
CBSEENPH11019935
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A boy standing on a stationary lift (open from above) throws a ball upwards with the maximum initial speed he can, equal to 49 m s-1. How much time does the ball take to return to his hands? If the lift starts moving up with a uniform speed of 5 m s-1 and the boy again throws the ball up with the maximum speed he can, how long does the ball take to return to his hands ?

Solution
Given comma space Initial space velocity space of space the space ball comma space straight u space equals space 49 space straight m divided by straight s Acceleration comma space straight a space equals space – space straight g space equals space – space 9.8 space straight m divided by straight s squared space Case space 1 colon space The space boy space throws space the space ball space when space the space lift space is space stationary. space Considering space that space the space motion space of space the space ball space is space upwards comma space final space velcoity space is space zero space at space the space highest space point. space Now comma space using space first space equation space of space motion comma space Time space of space ascent space is space given space by comma space space space space space space space straight v space equals space straight u plus at space rightwards double arrow space straight t space equals space fraction numerator left parenthesis straight v minus straight u right parenthesis over denominator straight a end fraction space space space space space space space space equals space fraction numerator negative 49 over denominator negative 9.8 end fraction space equals space 5 space sec Time space of space ascent space equals space time space of space descent. space Therefore comma space Total space time space taken space for space the space ball space to space return space to space the space boy apostrophe straight s space hands space equals space 5 space plus space 5 space equals space 10 space sec. 
Case 2: 

Speed space with space which space the space lift space is space moving space up space equals space 5 space straight m divided by straight s So comma space Relatiove space velocity space of space the space ball space is space the space same space as space it apostrophe straight s space initial space velocity. straight i. straight e. comma space straight v space equals space 49 space straight m divided by straight s Implies comma space the space ball space will space return space back space to space the space boy ’ straight s space hand space after space 10 space straight s.

Some More Questions From Motion in Straight Line Chapter

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.

Define distance.

Define displacement.

Can magnitude of displacement be greater than distance travelled by particle?

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