IIT JEE , AIEEE Forum - Physics , Mechanics - "TARGET IIT - JEE 2008 || CHALLENGING PROBLEMS FROM PHYSICS"

Avinash_Bhat

HI FRIENDS,

I WOULD TRY MY BEST TO GET THE BEST PHYSICS QUESTIONS THAT ARE OF THE SAME STANDARD AS THAT OF THE PRESENT IIT-JEE LEVEL AND WE SHALL HAVE RELATED DISCUSSIONS ON THEM.

HEY FRIENDS,

PLEASE GIVE YOUR ANSWER WITH FULL SOLUTION SO THAT EVERY VIEWER UNDERSTANDS IT WELL........

Avinash_Bhat

QN.1 Type : More than one of the options are correct.

Let F(X) be a conservative force. Under this force, a particle is displaced from the initial position X_i to final position X_f. Which of the following relations are correct?

(a) _Xi

^Xf F(X) dX = K_f - K_i(b) K_i + U (X_i) = K_f + U (X_f)

(c) - _Xi

^Xf F(X) dX = U (X_f) - U (X_i)

(d) | K_f - K_i | = | U (X_f) - U (X_i) |

rooney

I think all 4 are right. Conservative force conserves mechanical energy.So, (B) is right.

(c) is also right since its a well known formula.

Using (b) and (c), we get (a). And (b) automatically implies (d).

Sp, a,b,c,d are right.

Avinash_Bhat

QN.2 Type : Only one of the options is correct

A Physics textbook of mass m rests flat on a horizontal table of mass M placed on the ground. Let N_a-b be the contact force exerted by some body 'a' on some other body 'b'. According to Newton's 3rd law, which of the following is an action-reaction pair of forces?

(a) mg and N_table-book
(b) (m + M)g and N_table-book
(c) N_ground-table and Mg + N_book-table
(d) None of these

akhil_o

d? none of these

raulrag009

rooney

We have to consider the force it self and not its magnitude. And none of the pairs seem to be exerted from 1 body to the other and vice versa. So, D.

dream

its D

neeraj_agarwal_1990

yup...should be D....

Avinash_Bhat

Yes, the answer is D.

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