A block of mass m = 3.00 kg situated on a rough incline at an angle of = 37.0° is connected to a spring of negligible mass having a spring constant of 100 N/m (Fig. P8.58). The pulley is frictionelss. The block is released from rest when the spring is unstretched. The block moves 13.5 cm down the incline before coming to rest. Find the coefficient of kinetic friction between block and incline.
the figure can be seen here >> http://www.webassign.net/sb5/p8-58alt.gif
I'm assuming I want to use conservation of energy, but I'm just not really sure how to get it started... any help would be appreciated.
2006-10-10 09:47:40 · 1 answers · asked by flossie116 4 in Science & Mathematics ➔ Physics
First, I think the problem is unrealistic. (I'll discuss that later.) Second, conservation of energy gets too complicated when you have dissipative effects like friction.
When the block stops, the force parallel to the incline due to its weight, minus the friction force, is what stretches the spring. You know the spring force from k*x, you know the parallel force from m*g and the angle. These give you the friction force. You can find the normal force due to the block's weight from m*g and the angle. So you can compute the coeff. of friction.
My complaint about the problem centers on the assumption that the block has obligingly stopped sliding the instant the spring force exactly balances the downward mgSIN(theta) force minus the upward friction force. (Otherwise we couldn't solve the problem.) In real life, overshoot due to the inertia of the moving mass, followed by settling to an indeterminate position, is quite probable but here it didn't happen. How lucky.
2006-10-10 12:23:14 · answer #1 · answered by kirchwey 7 · 0⤊ 0⤋