- #1
Fyreth
- 8
- 0
Suppose we have two objects and we're only talking about rectilinear motion.
Initially, one object has mass m and is moving at velocity V. The other has mass M and is standing still.
Then they hit each other and suppose that all kinetic energy is conserved and they stick together and move at velocity v.
Then this follows from the conservation of energy:
1/2mV[itex]^{2}[/itex] = 1/2(m+M)v[itex]^{2}[/itex]
And this follows from the conservation of momentum:
mV = (m+M)v
But when we divide the first equation by the second one we get:
1/2V = 1/2v
V = v
Which implies that M is zero but I haven't stated that anywhere, at least not directly. What did I do wrong?
Initially, one object has mass m and is moving at velocity V. The other has mass M and is standing still.
Then they hit each other and suppose that all kinetic energy is conserved and they stick together and move at velocity v.
Then this follows from the conservation of energy:
1/2mV[itex]^{2}[/itex] = 1/2(m+M)v[itex]^{2}[/itex]
And this follows from the conservation of momentum:
mV = (m+M)v
But when we divide the first equation by the second one we get:
1/2V = 1/2v
V = v
Which implies that M is zero but I haven't stated that anywhere, at least not directly. What did I do wrong?