A 300 g bird flying along at 6.0 m/s sees a 10 g insect heading straight toward it at a speed of 30 m/s. The bird opens its mouth wide and enjoys a nice lunch. What is the bird’s speed immediately after swallowing?

Video transcript

Welcome back. Everyone in this problem. A 410 g cat is running at 4.1 m per second when it catches a 12 g mo running toward it at 22 m per second. What is the cat's speed? A sorry immediately after catching the most A says it's 1.2 m per second. B 3.4 m per second. C 6.4 m per second and D 7.1 m per second. If we're going to find the cat's speed immediately after catching the mouse. Let's make a note of the information we have so far. We know that the mass of the cat, let's call that MC C for cat is 410 g or 0.41 kg. Our cat is running at a speed VC of 4.1 m per second. Now, we know that it catches at 12 g moss. So the mass of the mos is 12 g are 0.012 kg. And it's running toward the cat at a speed of 22 m per second. So if we use the cat as the reference point, then the speed of the most is going to be negative 22 m per second. So we have our masses and our speeds. How can we use that to figure out the cat's speed after catching the mouse? Well, in this case, we can apply the law of conservation of momentum and recall that it says in a collision, the total momentum before the collision is equal to the total momentum after the collision. In other words, P is equal to PF where our momentum P is the product of the mass and the speed. So if we apply that idea, then if we think about our initial momentum before the cat and the mouse collided, then the total momentum there would be the mass of the cat multiplied by its speed plus the momentum of our mouse. OK. That's its mass multiplied by its speed and that would be equal to our final momentum. Now remember our problem tells us that the cat catches the most. So no, the cat is running but it also has the mass of the most. OK. So that momentum is going to be equal to their total mass, the mass of the cat and the mouse multiplied by the final speed. VF So now we can go ahead and solve because if we rearrange here to solve for our final speed, that means it equals M CV C plus mm MVM divided by MC plus mm. In other words, we've divided both sides by the sum of the mass of the cat. And the mouse from the right hand side of our equation. Now we can go ahead and substitute our values to serve the mass of the cat is 0.41 kg. The speed of the cat is 4.1 m per second. The mass of the most is 0.012 kg and its speed is negative 22 m per second. And now all of this is being divided by the sum of those masses which is 0.41 kg plus 0.012 kg. So not to solve for the final speed, we can go ahead and solve here. Now, when we substitute these values, then we should get the final speed to be equal to 3.3578 m per second. Notice all of our answers are written to two significant figures. And when we do the same, we get our final speed to be approximately equal to 3.4 m per second. Therefore, B is the correct answer. Thanks a lot for watching everyone. I hope this video helped.