Question

state the law of conservation of momentum prove it mathematically

Answer 1

Law of conservation of linear momentum :- when there is no any external force applied on a system of particles then , momentum of system of particles will be conserved or you can say that if external force is zero. Then momentum of system of particles in intially = momentum of system of particles in finally.
Mathematically,
From Newton's second law,
Fext = dP/dt
If Fext = 0, ∫ dP =∫ 0.dt
Means dP = 0
e.g., Pi = Pf


Let two bodies A and B of masses m₁ and m₂ are moving with velocities u₁ and u₂ , after collision velocities of bodies are v₁ and v₂ respectively.
Then, initial momentum of bodies ,Pi= m₁u₁ + m₂u₂
Final momentum of bodies, Pf = m₁v₁ + m₂v₂
Because external force doesn't apply here, so, linear momentum will be conserved .
e.g., Pi = Pf
m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂


[Note :- here doesn't include sign of velocity , but when you will solve question include direction of velocity as you know velocity is vector quantity

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.