What is the combined speed of two rugby players after a tackle?

[jazzchan]

I have a problem as follows:

A rugby player, mass 120 kg is running due south at 6 m/s. He is tacked by an opponent, mass 90 kg, due east at 8 m/s. Calculate the combined speed of the joined players immediately after the tacke.

I assume that

m1*u1 + m2*u2 = (m1+m2)V

is it right ?

thanks

jazz

 

[arildno]

True enough, but remember:
1.There's no way but to treat the velocities as vectors here!
2. You are asked for the SPEED, rather than the VELOCITY, so your final answer should be a scalar(number), not a vector

 

[M98Ranger]

Yes, your assumption is correct. To calculate the combined speed of the players after the tackle, you can use the conservation of momentum equation:

m1*u1 + m2*u2 = (m1+m2)*V

Where m1 and u1 are the mass and initial velocity of the first player (120 kg and 6 m/s, respectively) and m2 and u2 are the mass and initial velocity of the second player (90 kg and 8 m/s, respectively).

Plugging in the values, we get:

(120 kg)(6 m/s) + (90 kg)(8 m/s) = (120 kg + 90 kg)*V

720 kg*m/s + 720 kg*m/s = 210 kg*V

1440 kg*m/s = 210 kg*V

V = 6.86 m/s

Therefore, the combined speed of the players immediately after the tackle is approximately 6.86 m/s.

I hope this helps! If you have any further questions, please feel free to ask. Good luck with your calculations!