IIT JEE , AIEEE Forum - Physics , Mechanics

(0)

pleaz.,............ solve it fully

Q. A metal sphere is hung by a string fixed to a wall. The forces acting on the sphere are shown in figure. Which of the following statement is not correct

A	T = R + W
B	T2 = R² + W²
C
D	R = W tan

rooney

A

Balance forces in vertical and horizontal axis,
TCos

=W
TSin

=R
Adding
T (Cos

+ Sin

) = W + R
T=(W+R)/(Cos

+ Sin

) which is not equal to W+R

tka

let the angle be @.

in equilibrium, we can equate forces in vertical and horizontal components.

Tsin@ = R ----1

Tcos@ = W -----2

a. square and add the two equations.

T^2 = R^2 + W^2

this gives us option B. but for this to be equal to option A, one of the forces must be zero. so option A is wrong, and option B is right..

b. the forces are in equilibrium.

T + R + W = T + (-T) = 0

option c is correct.

c. divide the two equations.

tan@ = R/W

R = Wtan@

so option D is right.

answer - a

karthik2007

@rooney - I think the first option represents vectorial addition... if it were true, there comes an ambiguity in option c)

tka

oye T = (-R)+ (-W) = -(R+W)

and not R+W

(like u said, by vectorial addition)

A is the wrong option

karthik2007

tka

...but i mathematically proved that option B is always right!

yaar please have a look ar my proof above and spot the mistake if any

karthik2007

Sorry... It is option a)

made a major blunder... yes you guys are perfectly right

bhartibhanushali

its option c
by parallelogram of addition
T = -[r+w]
t+r+w =o

tka

OYE YAAR read the question carefully .

C is a correct option - even B and D are correct - the question is asking for the WRONG OPTION, WHICH IS A

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