can anyone please help me with this question? i already try for part a but i dont have any idea for part b..i need to submit the answer before wednesday.. thank you in advance

Question

2. An object of mass 5 kg travels in a straight line at 4 ms^-1. It collides with an object of mass    7 kg traveling in the same direction at 2 ms^-1. Calculate the

a)   Total momentum before collision. (2 marks)

Momentum before =

                          

                             = (5) (4) + (7) (2)

                             

                             = 34  

b)   Final velocity if they move together after the collision. (2 marks)

Answer 1

So Adleena H.,

you showed correct work for part (a); good, that gets you help for (b)!

You probably recall that, in all collisions (and everywhere in the universe, in fact), momentum is conserved. That means, in any problem, the initial total momentum is the same as the final total momentum.

Therefore, when you computed your initial total momentum, you also computed your total final momentum. But, you say, I need a velocity! Sure; P (momentum) = m (mass) * v (velocity)

So you know P, and you know m (the two masses stick together, so how do you figure total mass? That should be a "no - brainer"). Then you just do the division, to get v (the final combined object velocity). Oh, don't forget to round to proper significant digits -- just to be on the safe side, express that once as exact (2+⁵/₆) and once rounded to 1 SigFig. Don't forget proper units, too -- numbers are meaningless without units!

i think that's all you need here.

--Cheers,- Mr. d.

Answer 2

You find the solution by equating momentum before of both objects and momentum after (total momentum conserved in a collision). In symbols:

m₁v₁ + m₂v₂ = (m₁ + m₂) v₁₂

Just solve for v₁₂ which is the velocity of 1 and 2 together. Since the carts are going in the same direction all signs are positive.