- #1

roam

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## Homework Statement

[PLAIN]http://img237.imageshack.us/img237/6677/incline.gif [Broken]

A snow sled with a child secured safely to it has a total mass of 83.0 kg. It is lowered at a constant speed of 1.9 ms

^{−1}down a slope of angle 41.0° with respect to the horizontal (as shown above) for a distance d = 14.0 m. The coefficient of kinetic friction between the sled and the snow is 0.09.

g = 9.8 ms

^{–2}. Air resistance is negligible at these speeds.

I have calculated the friction force to be 55.3, and the magnitude of the reactive force, N, on the sled to be 614.49 Newtons.

Then the question asks:

Suppose the rope suddenly snaps at its point of connection with the sled after travelling the distance d. Determine the drag force acting on the sled when it reaches a terminal speed of 8.4 ms

^{−1}.

## The Attempt at a Solution

What does the question mean by the "drag force acting on the sled "? Is it reffering to the force that pulls the sled down the incline? I know that force is equal to

[tex]mg sin \theta = (83 \times 9.81) sin(41)= 534.18[/tex]

But this is wrong because the correct answer has to be

**478 N**.

Another approach I can think of is to find the time using dv=t= 117.6 and acceleration by [tex]a=v/t \Rightarrow a =\frac{8.4}{117.6}=0.07[/tex] then plug this into [tex]\sum F_x=ma_x=83 \times 0.07=5.9[/tex]. Which is again wrong...

Can anyone help?

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