why does a spark jump from your hand to the doorknob as you reach for the door after walking across a carpeted floor?
2 answers:
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The momentum increases by a factor of 2
Explanation:
We can solve this problem by rewriting the momentum of the rocket in terms of the kinetic energy and the mass.
The kinetic energy of the rocket is:
(1)
where
m is the mass
v is the velocity
The momentum of the rocket is
(2)
From eq.(1) we get
and substituting into (2),
Now in this problem we have:
- The kinetic energy of the rocket is increased by a factor 8:
- The mass is reduced by half:
Substituting, we find the new momentum:
So, the momentum increases by a factor of 2.
Learn more about momentum and kinetic energy:
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Car X traveled 3d distance in t time. Car Y traveled 2d distance in t time. Therefore, the speed of car X, is 3d/t, the speed of car Y, is 2d/t. Since speed is the distance taken in a given time.
In figure-2, they are at the same place, we are asked to find car Y's position when car X is at line-A. We can calculate the time car X needs to travel to there. Let's say that car X reaches line-A in t' time.
Okay, it takes t time for car X to reach line-A. Let's see how far does car Y goes.
We found that car Y travels 2d distance. So, when car X reaches line-A, car Y is just a d distance behind car X.