+0  
 
+5
775
2
avatar+1313 

I'm having trouble nutting out the accurate answer even though I can follow the steps I'm making a mistake somewhere, though it should be correct. Perhaps in the calculator but I'd like to see the math behind it. 

v1 = 17 m/s east, v2 = 0. (not sure how velocity without dirrection but ok.)
after the collision v1 is -45 degrees and v2 is 30 degrees. 

I calculated the x velocities and y velocities using momentum formula, then substitued the y-velocities 1/2 equation in for v1 (or v2) and I got the answer wrong when substituting in as v1 as well as for v2. 

Answer is v1= 8.8 m/s and v2 = 12.4 m/s. 

I had skype assistance with this earlier, they could do this easy but got v2 correct and v1 as 0. The step 3 is to put the answer back in to the equation but im not sure at what step, and have not done it because my answers are comming up wrong even with the answers in front of me. So I'm just after a more detailed explaination as the answers(calculations I have) are missing a lot of information. 


Any ideas?


 Jul 16, 2014

Best Answer 

 #2
avatar+1313 
+5

Yes you are right it can be solved easily enough but I still got it wrong. I checked my maths a few times. I think it is calculator input.

 Jul 16, 2014
 #1
avatar+33661 
+5

With the assumption that both masses are equal and momentum is conserved the momentum equations can be written as:

Horizontal:   17 = v1*cos(45) + v2*cos(30)

Vertical:         0 = -v1*sin(45) + v2*sin(30)

These can be solved easily enough to find v1 ≈ 8.8 and v2 ≈ 12.4

However, this must be an inelastic collision, because kinetic energy is not conserved.  That is 1/2*172 ≠ 1/2*v12 + 1/2*v22.

 Jul 16, 2014
 #2
avatar+1313 
+5
Best Answer

Yes you are right it can be solved easily enough but I still got it wrong. I checked my maths a few times. I think it is calculator input.

Stu Jul 16, 2014

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