B-80
- 73
- 1
The only force acting on a 1.9 kg body as it moves along the positive x-axis has an x component Fx = - 6x N, where x is in meters. The velocity of the body at x = 3.0 m is 8.0 m/s.
(a) What is the velocity of the body at x = 4.0 m?
well work is the integral of the f(x) function, so its -3x^2. Knowing that I can get the work done from x=3 to x=4. which is -3*9 and -3*16. after omitting the sign, which I figured I need to do after about an hour of this problem, I get a net change of 21J. so I plug that into 1/2MVf^2-1/2MVi^2 and get 1/2M(Vf^2-Vi^2)=21J
21J/(.5*1.9Kg)=Vf^2-Vi^2
22.105+Vi^2=Vf^2
Vf=sqrt(22.105+8^2)
this yields me an answer of 9.28 m/s
I must have done this problem about 8 times now, and I can't get it right.
(b) At what positive value of x will the body have a velocity of 5.0 m/s?
(a) What is the velocity of the body at x = 4.0 m?
well work is the integral of the f(x) function, so its -3x^2. Knowing that I can get the work done from x=3 to x=4. which is -3*9 and -3*16. after omitting the sign, which I figured I need to do after about an hour of this problem, I get a net change of 21J. so I plug that into 1/2MVf^2-1/2MVi^2 and get 1/2M(Vf^2-Vi^2)=21J
21J/(.5*1.9Kg)=Vf^2-Vi^2
22.105+Vi^2=Vf^2
Vf=sqrt(22.105+8^2)
this yields me an answer of 9.28 m/s
I must have done this problem about 8 times now, and I can't get it right.
(b) At what positive value of x will the body have a velocity of 5.0 m/s?