- #1
PhysicsKid0123
- 95
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[Mentor's note: This post does not use the homework-forums template because it was originally posted in one of the discussion forums. I moved it here instead of deleting it because it already had several answers in the spirit of the homework-forum rules.]
Okay so I am having a hard time wrapping my head around this. Before looking at the answer I worked the example and got the answer only because I used dimensional analysis to get me to the right units for force. However, to be honest, I don't think I even understand the concept here. I know mass is changing and velocity is constant, but what is throwing me off is where it says "The water strikes the window at 32 m/s so each kilogram of water loses 32 kg.m/s of momentum. Water strikes the window at the rate of 45 kg/s, so the rate at which it loses momentum to the window is... 1400kg m/s^2" How is it losing 32 kg m/s of momentum and then at the same time also losing it at a rate of 1400 kg m/s^2? Why does it even mention "The water strikes the window at 32 m/s so each kilogram of water loses 32 kg.m/s of momentum" what is the purpose of that sentence. That is really confusing me.
I added this simple diagram to show how I see this system. Where is 32 kg. m/s of momentum come in? (I am aware that the window is now showing)
Okay so I am having a hard time wrapping my head around this. Before looking at the answer I worked the example and got the answer only because I used dimensional analysis to get me to the right units for force. However, to be honest, I don't think I even understand the concept here. I know mass is changing and velocity is constant, but what is throwing me off is where it says "The water strikes the window at 32 m/s so each kilogram of water loses 32 kg.m/s of momentum. Water strikes the window at the rate of 45 kg/s, so the rate at which it loses momentum to the window is... 1400kg m/s^2" How is it losing 32 kg m/s of momentum and then at the same time also losing it at a rate of 1400 kg m/s^2? Why does it even mention "The water strikes the window at 32 m/s so each kilogram of water loses 32 kg.m/s of momentum" what is the purpose of that sentence. That is really confusing me.
I added this simple diagram to show how I see this system. Where is 32 kg. m/s of momentum come in? (I am aware that the window is now showing)
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