Looking for verification on a momentum & collision problem

  • Thread starter Thread starter PHYclueless
  • Start date Start date
  • Tags Tags
    Collision Momentum
AI Thread Summary
The discussion centers on a momentum and collision problem involving two runners with specified masses and velocities. The initial momentum calculations yielded 300 kg·m/s for Runner 1 and -320 kg·m/s for Runner 2. The user attempted to determine the final velocity and direction after a perfectly inelastic collision but faced confusion in their vector algebra. Feedback indicated that the user should apply cosine for the x-component and sine for the y-component in their calculations. The overall conclusion is that while the method is correct, the application of trigonometric functions needs adjustment for accurate results.
PHYclueless
Messages
7
Reaction score
0
Here is the problem:
Runner1 is going 20 degrees NofE with a mass of 60kg and v=5m/s. Runner2 is going 20 degrees NofW with a mass of 80kg and v=4m/s when they collide. What are their respective momentums prior to the collision? What is their final velocity and direction after collision if it was perfectly inelastic collision?

For question1 I got L=300kgm/s for runner1 and L=-320kgm/s for runner2.

For question2 I'm a little perplexed. This is what I did.
(x) m1v1+m2v2=(m1+m2)vf
-4sin20(80kg)+5sin20(60kg)=(60kg+80kg)vf
-109+103=140vf
-6=140vfx
vf(x)=-.049m/s

(y) m1v1+m2v2=(m1+m2)vf
4cos20(80kg)+5cos20(60kg)=(60kg+80kg)vf
301+282=140vf
583=140vf
vf(y)=4.16m/s

Then I took the TAN-1(4.16/-.049) to find theta and it gave me -89degrees North of East.

Does this look right?

Thank you to anyone who can give me some insight. I appreciate your help.
 
Physics news on Phys.org
Your method is right.
But your vector algebra is slightly flawed.
For (x) take cosine and not sine.
Viceversa for (y) .
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'Calculation of Tensile Forces in Piston-Type Water-Lifting Devices at Elevated Locations'
Figure 1 Overall Structure Diagram Figure 2: Top view of the piston when it is cylindrical A circular opening is created at a height of 5 meters above the water surface. Inside this opening is a sleeve-type piston with a cross-sectional area of 1 square meter. The piston is pulled to the right at a constant speed. The pulling force is(Figure 2): F = ρshg = 1000 × 1 × 5 × 10 = 50,000 N. Figure 3: Modifying the structure to incorporate a fixed internal piston When I modify the piston...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top