Help needed urgently...........................?

Question

two objects A and B of respectiv masses Ma = 8 kg, Mb = 2kg
are travelling towards each other along the x-axis with
velocities ua = 40 ms^-1 and ub = 5 ms^-1, when they collide
and coalesce into a single object

After the collision the combined object moves along the x-axis
How much energy is lost in the collision?

Answer 1

let final velocity of combined object be v
by conservation of linear momentum
8(40)-(2)(5)=10(v)
v=31ms^-1
energy lost= 0.5(8)(40^2)+0.5(2)(5^2)
-0.5(10)(31^2)=1620J

Answer 2

Calculate momentum (mv) and kinetic energy (mv²/2). Momentum is ALWAYS conserved, but kinetic energy isn't always (sometimes it turns into heat).

Total momentum before = Total momentum after
(80kg)(40m/s) – (2kg)(5m/s) = (80kg+2kg)(V_after)

(I _subtracted_ on the left side because it said they're traveling "towards each other," which means that one velocity's positive and the other is negative.)

The value on the right side represents the momentum of the coalesced "lump." You should be able to solve for V_after.

Now that you have all the V's and all the m's, use the formula mv²/2 to calculate the total kinetic energy before, and compare it to the total energy after. The difference is the amount of energy that was lost.

Answer 3

hmm.. i don't know... a lot?
i used to know this stuff...
used to