PDA

View Full Version : Collision and Momentum of these two birds


xmirxtimex
Jun 28, 2009, 07:10 PM
Two birds of prey hurtling after the same mouse collide in mid-air and grab each other with their talons. If each 250 g bird is flying at 30 m/s at a 60° angle to the ground, what is their total momentum, in (kg*m)/s, immediately after the collision?
a. 0
b. 6.5
c. 7.5
d. 13
e. 15


Similar question to above:

Two birds of prey hurtling after the same mouse collide in mid-air and grab each other with their talons. If each 250 g bird is flying at 30 m/s at a 60° angle to the ground, what is the horizontal component of their momentum, in , immediately after the collision?

a. 0
b. 6.1
c. 7.5
d. 13
e. 15

Perito
Jun 28, 2009, 08:10 PM
Separate the birds' speed and mass into horizontal and vertical components. The sum of the momentum components in the horizontal direction add to give the answer you seek.

xmirxtimex
Jun 28, 2009, 08:13 PM
For the total momentum, I got 0.

For the Horizontal, I got 7.5.

Are these correct? Or am I way off?

Perito
Jun 28, 2009, 08:21 PM
The problem doesn't state it, but they do collide so I assume they are flying toward each other. I'm assuming that each makes a 60 degree angle with the ground, but the angles face each other.

Momentum = MV = 0.25 Kg x 30 m/sec = 7.5 kg m/sec

Horizontal component of momentum = 7.5 cos (60) = 3.75 Kg m/sec

3.75 + 3.75 = 7.5 Kg m/sec

That's the answer for the Horizontal and so yours looks like that's correct. Note that the problem is equivalent to a 500 g bird flying at double the speed into an immovable wall.

Since the birds are now at rest (figuratively and literally speaking ;) ) , their momentum is zero, as you stated.

xmirxtimex
Jun 28, 2009, 08:29 PM
Thank you so much

Unknown008
Jun 29, 2009, 12:22 PM
I'd like to point out that in the first question, if the birds are flying towards each other, forming a 'V' figure, the vertical component of the total momentum won't be zero...

The horizontal however would have course be zero.