Why am I wrong? http://prntscr.com/96i0mk

Question

anonymous · Answer

can u help me please?

anonymous · Answer

well after this XD

parthkohli · Answer

Clearly, $f_{max} = \mu mg = 0.5 \times 10 \times 10  N= 50 N$ is greater than $F=40 N$, which suggests no displacement.

anonymous · Answer

Maybe a glitch in the system? it seems right to me.

imqwerty · Answer

the box will not move. D will be correct

parthkohli · Answer

imqwerty, more doubts. help.

imqwerty · Answer

okay i'll try

parthkohli · Answer

I think many answers are wrong. Try this question.

In how many ways can 5 boys and 5 girls sit in a circle so that no two boys sit together?

parthkohli · Answer

Give the answer in terms of factorials.

imqwerty · Answer

4! x5!  ?

welshfella · Answer

5!*5!  ?  I'm not very good at these...

parthkohli · Answer

http://prntscr.com/96iidq look at this!

parthkohli · Answer

Now a few questions I'm a little doubtful about. Like I'm not sure if my answer is correct.

imqwerty · Answer

:/ thats clearly wrong

parthkohli · Answer

A mass m is thrown as a projectile. The magnitude of its angular momentum about the highest point of trajectory above the ground:

A
Is zero
B
Remains constant
C
First decreases and then increases
D
Goes on decreasing

parthkohli · Answer

Do you agree that at the highest point itself, the angular momentum about the highest point is zero?

parthkohli · Answer

Now look at|dw:1448394824352:dw| the beginning of the trajectory.