## King Group Title A baseball player hits a homerun, and the ball lands in the left field seats, which is 120 m away from the point at which the ball was hit. The ball lands with a velocity of 20 m/s at an angle of 30 degrees below horizontal. Ignoring air resistance (A) find the initial velocity and the angle above horizontal with which the ball leaves the bat; (B) find the height of the ball relatively to the ground 2 years ago 2 years ago

1. Mani_Jha Group Title

If there is no air resistance, the parabolic path will be symmetrical, and thus it will land at the same velocity with which it left. So $u=20 m/s and \theta=30$ The height will be $h=u ^{2}\sin ^{2}\theta/2g$

2. salini Group Title

it is like that concept in which when u fire a bullet vertically up,it comes down same straight line to hit u with same speed with which it went if not for air drag

3. salini Group Title

there is a common principle that when a body is thrown up from a certain height,then when it comes back to the same height, it will have the same velocity

4. salini Group Title

|dw:1328876734968:dw||dw:1328876550335:dw| sincew the magnitude of velocity is same however when u see the angle made with the horizontal,first it is theta and next it is 189-theta

5. salini Group Title

sorry 180-theta*

6. King Group Title

ya so ?

7. salini Group Title

wat is your doubt in this?

8. King Group Title

i dont understand wat is the answer and hw u got it?....i only understood the same velocity thing

9. King Group Title

and also in the website there are numerical answers but we didn't get any?

10. King Group Title

and can u pls xplain with numerics b'cuz i hate variables in physics and dont understand it

11. salini Group Title

|dw:1328877186942:dw| is the question like this or are the bat and ball at the same level?

12. King Group Title

no its a parabola same height

13. King Group Title

|dw:1328877374070:dw|

14. salini Group Title

ok now first draw the diagram with all velocities, distance marked in it with wat u understood

15. King Group Title

|dw:1328877495107:dw|

16. salini Group Title

in A portion,they ask for angle made with horizontal which is 30 as i explained and the magnitude of velocity is same 20m/s dont bother about the direction being different as when we say that a vector has magnitude and direction, we mean to say that we can write it in terms of i^ j^ k^ anyway my magnitude of velocity remains the same if u want to write that velocity in terms of components i can teach u how to do it the u get a solid vector notation of the velocity when ball leaves bat

17. King Group Title

ok...can u teach me hw to write in terms of components?

18. salini Group Title

|dw:1328877872806:dw| give me the values for vx and vy

19. King Group Title

vy=2cos30 or 20cos30?

20. King Group Title

salini?

21. salini Group Title

value

22. King Group Title

is it 2cos30 or 20cos30 i cant understand..if u tell me that i will calculate the value

23. salini Group Title

20*root3/2 and 20*1/2

24. King Group Title

i meant it looked like 2cos30

25. King Group Title

it is 10sqrt3 and 10

26. salini Group Title

|dw:1328878380008:dw|where i and j are direction along x and y axis and are mutually perpendicular to one another

27. King Group Title

do u hav to use i cap and j cap?

28. salini Group Title

AND THATS HOW U REPRESENT ANY VECTOR YES U HAVE TO TO SPECIFY DIRECTIONS

29. King Group Title

hey why u gettin angry?i am not ud at those and we hav to find only magnitude anyways..if u are irritated and dont wanna explain its fine

30. King Group Title

*gud

31. salini Group Title

no I turned the capslock when i answered arvind

32. King Group Title

oh!sry!

33. King Group Title

sry salini i shall try frm here on my own...rite nw i gtg!