Physics: Post your doubts here!

A

amal sharkawi

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Thought blocker said:
vertical velocity= u cos 45
horizontal velocity = u sin 45
so, initial K.E. : the vertical and horizontal components of kinetic energy = 1/2 m ( u cos 45 ) + 1/2 m ( u sin 45 ) ......... ( 1/2 m v^2 formula )

so, sin 45 = 0.71
....cos 45 = 0.71 ( check them in the calculator )

so they will give the same kinetic energy for both velocities ( horizontally and vertically )

so at the highest point, (theta) = 90 ( for the vertical velocity ) , horizontal velocity doesn't change
so final kinetic energy = 1/2 m ( u cos 90 ) + 1/2 m ( u sin 45 )..................... ( horizontal velocity is constant ) ( cos 90 is 0 )
final kinetic energy = 1/2 m ( u sin 45 ) + 0 only which is half of the initial kinetic energy.
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ZaqZainab

ZaqZainab

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chishtyguy

chishtyguy

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selena said:
Answer is B but I don't know how
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My mistake... Answer is B... It's the cell with which the voltmeter is connected not the resistor... So Emf coming out of the cell and across the 15 ohm resistor is 7.5V... Then by using the formula I=V/R =7.5/15 , we will get .5 A current...
 
Hadi Murtaza

Hadi Murtaza

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Last edited:
Hadi Murtaza

Hadi Murtaza

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Hadi Murtaza said:
q.9

Displacement is distance from starting point regardless of how much da body has travelled.

Distance from 0 to 3 s is (1/2) * 3 * 30 = 45 m

Distance from 3 to 5 is (1/2) * 2 * -20 = -20 m

So final distance from starting point = 45 - 20 = 25 m
Answer: B
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Der is another way of solving dis too but its slightly more complicated
 
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