http://www.webassign.net/giocp1/4-p-043.gif How long does it take for the sled t

Question

http://www.webassign.net/giocp1/4-p-043.gif How long does it take for the sled to reach a speed of 12 m/s? http://www.webassign.net/giocp1/4-p-043.gif How long does it take for the sled to reach a speed of 12 m/s? How long does it take for the sled to reach a speed of 12 m/s? How long does it take for the sled to reach a speed of 12 m/s?

Explanation / Answer

First, you need to find the forces in each direction of the two people pulling the sled. Lets say Larry is pulling at 15N and Moe is pulling at 10N. Larry pulls the sled in the x-direction: cos(30) = Lx/15N --> 15 * cos(30) = Lx; where Lx stands for Larry in the x direction. and in the y direction: sin(30) = Ly/15N --> 15 * sin(30) = Ly; Ly is Larry in the y-direction. ** you should get values of Lx = 13N, Ly = 7.5N, but these are slightly rounded ** Now for Moe in the x-direction: cos(50) = Mx/10N --> 10 * cos(50) = Mx; and in the y-direction: sin(50) = My/10N --> 10 * sin(50) = My; ** you should get values of Mx = 6.43N, My = 7.66N ** As you see, the y components should just about cancel out, which leaves you with a nice simple problem. All you need to do is add the forces in the x direction: Lx + Mx = F = ma; where m=13kg. Solve for acceleration, a. ** your value should be about 1.5 m/s^2 ** Now use the velocity equation v = v0 + at; v0 is initial velocity, v is final velocity. v0 = zero here, a = 1.5, v = 12. Solve for t. Units work out fine, no worries. Hope this helped.

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