Net Force and Friction

[TheBurningMan]

I'm new, so I'd like to say thanks in advance for helping me. The site wants all answers to the 4th decimal place. Idk how stuff normally works around here, but a small explanation with the answer would help me understand this stuff better.

1. Three forces act on a particle that moves with an unchanging velocity v = (6 m/s) i - (7 m/s) j. Two of the forces are FA = (4 N) i + (5 N) j + (-2 N) k and FB = (-5 N) i + (8 N) j + (-4 N) k. What is the third force?

_____N i + _____N j + _____N k

2. A baseball player with mass m = 76 kg, sliding into second base, is retarded by a frictional force of magnitude 500 N. What is the coefficient of kinetic friction µkin between the player and the ground?

_____



2. I'm unsure because I missed class with an awesome case of food poisoning. -_-



3. I was sick in class, so I'm unsure.

[Google_Spider]

1. F_A+F_B+F_C=0
2. f=\mu_kN

[olgranpappy]

I'm new, so I'd like to say thanks in advance for helping me. The site wants all answers to the 4th decimal place. Idk how stuff normally works around here, but a small explanation with the answer would help me understand this stuff better. p.s. my bad for posting this in both forums, but I'll delete the threads as soon as I learn this stuff. Thanks again..

1. Three forces act on a particle that moves with an unchanging velocity v = (6 m/s) i - (7 m/s) j. Two of the forces are FA = (4 N) i + (5 N) j + (-2 N) k and FB = (-5 N) i + (8 N) j + (-4 N) k. What is the third force?

_____N i + _____N j + _____N k

2. A baseball player with mass m = 76 kg, sliding into second base, is retarded by a frictional force of magnitude 500 N. What is the coefficient of kinetic friction µkin between the player and the ground?

_____



2. I'm unsure because I missed class with an awesome case of food poisoning. -_-


Ah. Life is suffering. And that's the good part.


3. I was sick in class, so I'm unsure.

Well, I guess the equation you missed which relates weight to frictional force would be

F_{\rm fric}=\mu_{\rm kin} m g


and for the first question the equation you missed was Newton's First (or is it the 2nd?) Law: A body in uniform motion remains in motion unless acted upon by a (net) Force. Thus the third force you seek must be that which cancels completely the other two.

[olgranpappy]

P.S. I think this thread should be in the Introductory Physics forum.