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Grade 9Mechanics

A ball is thrown vertically upwards with speed u from the top of a tower reaches the ground in 9 seconds.Another ball is thrown vertically downwards from the same position with same speed u takes 4 sec to reach ground. Calculate the value of u. Please please please help 🙏🙏🙏🙏

anuj

7 Years agoGrade 9

2 Answers

Saurabh Koranglekar

Approved Tutor Answer7 Years ago

Khimraj

7 Years ago

take 1st ball be b1 and another be b2.

ac/eq of motion

v=u+at

for b1

v=0(at highest height)

0=u-10×9(in case of of upward direction)

u=90m/sec

for b2, in this case final velocity is "u" since,

v=u + gt

=0+10×4

v=40m/sec

so,u1=90m/sec& u2=40m/sec

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