Question

A contender in a winter sporting meet pulls a 41kg block of ice in the positive horizontal direction with the cord over his shoulders over a frozen lake. Assume the coefficients of static and kinetic friction is us=0.1 and uk=0.03.

Calculate the minimum force F he must exert to get the block sliding in newtons?

What is the acceleration in m/s^2 once it starts to move, if that force is maintained?

Please show your work it will help me to figure out where I am going wrong with this problem.

Answer 1

I am trying to solve both parts of your question.

(a) Normal force, Fn = mg

= 41 kg * 9.8m/s² = 401.8 N

At the threshold, the static friction force is equal to the horizontal component of the applied force:

µs*Fn = Fmin

=> Fmin = 0.1 * 401.8 = 40.18 N (Answer)

Therefore, the minimum required force to get the block sliding = Fmin = 40.18 N (Answer)

(b) In this condition, we will calculate Fnet.

Fnet = Fmin - µk * Fn

= 40.18 - 0.03 * 401.8 = 40.18 - 12.05 = 28.13 N

Therefore, acceleration of the ice block, a = Fnet / m

= 28.13 N / 41 kg = 0.69 m/s² (Answer)