## Aadarsh 2 years ago A projectile is thrown horizontallly from the top of a tower and strikes teh ground after 3 second at an angle of 45 degrees with the horizontal. Find the height of the tower and speed with which the body was projected. (Take "g" = 9.8 m/s^2)

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3. srinidhijha

what is angle of projection? is the question written as it is?

Yeah, the question is as it is as I have written here.

5. srinidhijha

k

6. apoorvk

So when it strikes, basically the horizontal and vertical components of its velocity are equal (since it strikes the ground at 45 degrees) Now, let the initial velocity of projection be 'u' Now, the horizontal speed remains constant, but the vertical component increases from '0' to 'u', as it hits the ground. Now, vertical component (final) = v time of flight = sqrt(2gh) = 3 Find height, and then find 'u'.

How time of flight = sqrt(2gh)? Can u show the complete steps and other equations also?

8. apoorvk

LOL sorry - it would 'final' velocity, not time of flight - my bad lol.

Still i am not able to follow how is it equal to sqrt(2gh)? Can u show the workign of other steps also?

10. apoorvk

yeah, so use, (v-u)/g = t

11. srinidhijha

hey is the speed 97 ? u know the answers?

13. apoorvk

for a particle under free fall with initial velocity 'u=0'|dw:1338565657495:dw|

Got it. Can we not say that:$T = 2u \cos \theta / g = \sqrt{2}u/g$

15. apoorvk

yeah, v=30, and height = 45 metres, right?

16. apoorvk

well, that is for a ground-to-ground projectile @Aadarsh

@apoorvk bhai, ur answer is right.

@apoorvk bhai, please show all the steps.

19. srinidhijha

look the pa

Thanks apoorv bhai.

21. apoorvk

See, ye samajh mein aaya ki horizontal and vertical components at the time of hitting the ground same honge?

Yeh to samajh mein nahion aaya.....

samjha dijiye

24. srinidhijha

see the attachment koi horizontal equal lene ki jarurat nh ihai

25. srinidhijha

samajh aaya?

26. srinidhijha

isse pahle bhi ek attachment tha jisme U nikaala hai , dkho, Final velocity to 0 hi hoga naa jab wo gir jaaye to

Thakns srini bhaiiiiiiiii. samajh mein aa gaya.

28. srinidhijha

k good

29. apoorvk

Sri, great calligraphy! :P

30. AravindG

srry i am late :P

31. srinidhijha

ha ha