Question

explain law of conservation of angular momentum

Answer 1

Law:  When there is no external torque acting on a system of bodies, then the angular momentum of the system is a constant (wrt time or motion).

vectors:    angular momentum = L = r X p = m r X v
      dL/dt = r X dp/dt = r X F = Torque

Suppose we have a satellite orbiting around the EArth.  The satellite experiences a radial force ie., a gravitational force along the radius of  its orbit.  Then the torque is 0 as  r and F are along the same line.
        Hence L is a constant.

Answer 2

ᴀɴsᴡᴇʀ࿐

ᴅᴇғɪɴɪᴛɪᴏɴ:-

ᴍᴏᴍᴇɴᴛᴜᴍ ɪs ᴛʜᴇ ᴛʜᴇ ᴀᴍᴏᴜɴᴛ ᴏғ ᴍᴏᴛɪᴏɴ ᴏғ ᴀ ᴍᴏᴠɪɴɢ ʙᴏᴅʏ, ᴍᴇᴀsᴜʀᴇᴅ ᴀs ᴀ ᴘʀᴏᴅᴜᴄᴛ ᴏғ ɪᴛs ᴍᴀss ᴀɴᴅ ᴠᴇʟᴏᴄɪᴛʏ.

=>ᴍᴏᴍᴇɴᴛᴜᴍ= ᴍᴀss × ᴠᴇʟᴏᴄɪᴛʏ

ᴅɪᴍᴇɴsɪᴏɴᴀʟ ғᴏʀᴍᴜʟᴀ ᴏғ ᴍᴏᴍᴇɴᴛᴜᴍ

=>ᴘ = [ᴍ]x [ʟᴛ^(-1)]

ᴄᴏɴsᴇʀᴠᴀᴛɪᴏɴ ᴏғ ᴍᴏᴍᴇɴᴛᴜᴍ:-

ʟᴀᴡ ᴏғ ᴄᴏɴsᴇʀᴠᴀᴛɪᴏɴ ᴏғ ᴍᴏᴍᴇɴᴛᴜᴍ ɪs ᴅᴇғɪɴᴇᴅ ᴀs ᴀ ᴘʀɪɴᴄɪᴘʟᴇ ɪɴ ᴘʜʏsɪᴄs ᴛʜᴀᴛ sᴛᴀᴛᴇs ᴛʜᴀᴛ ғᴇᴡ ᴘᴀʀᴛs ɪɴ ᴀɴ ɪsᴏʟᴀᴛᴇᴅ sʏsᴛᴇᴍ ʀᴇᴍᴀɪɴɪɴɢ sᴛᴇᴀᴅʏ ᴀɴᴅ ᴜɴᴄʜᴀɴɢɪɴɢ ᴏᴠᴇʀ ᴛɪᴍᴇ ᴇᴠᴇɴ ᴡʜᴇɴ ᴏᴛʜᴇʀs ᴀʀᴇ ᴍᴏᴠɪɴɢ.