00:01
In this question, it says that we have to close an open door using either a clay or a ball, rubber ball.
00:09
So what we are doing is we have a clay of mass 400 grams and a similar rubber ball of mass, same mass 400 grams.
00:18
And we throw both of them with same velocity u1.
00:22
So we are taking their initial velocity as u1 and it is same for both.
00:27
Mass is also same for both.
00:29
Now we throw them to the door.
00:33
The clay sticks to the door after collision, whereas for the rubber ball, it will have an elastic collision with the door and it will move in the opposite direction.
00:50
It will come back after colliding with the door.
00:52
And we have to find out which one of them will impart higher impulse to the door and which one will be successful.
01:00
In being able to close the door.
01:03
So let us consider that the door mass is m2 and initially since the door is at rest so u2 the initial velocity of door is u2 which is zero.
01:12
Now finally after colliding either will clay or the rubber ball its velocity is v1.
01:20
Sorry, v2 it should be v2 so this is the final velocity of the door which is v2.
01:25
Now let us consider the two cases and find out the impulse imparted in both the cases and find out which one will be greater.
01:32
So for the case of clay we have the initial momentum that we have which is m1 and u1 and finally it will the clay sticks to the door of mass m2 and starts moving with the same velocity.
01:45
Since we have the momentum conserved even in this inelastic collision so we can use the momentum conservation here and it gives us the initial momentum which is m1 times u1 plus m2 times 0 this will be equal to m1 plus m2 because both of them together moving with same velocity which is v2 final velocity of the door and it will be same for the clay so this is the momentum conservation equation from this we can find out v2 which will be equal to m1 u1 divided by m1 plus m2 so this is the final velocity of the door door after being after we throw the clay to it.
02:35
So the impulse imparted to the door will be impulse will be equal to the change in momentum of the door.
02:50
That is always true...