In your physics lab, a block of mass m is at rest on a horizontal surface. You a
ID: 1331529 • Letter: I
Question
In your physics lab, a block of mass m is at rest on a horizontal surface. You attach a light cord to the block and apply a horizontal force to the free end of the cord. You find that the block remains at rest until the tension T in the cord exceeds 20.0 N. For T > 20.0 N , you measure the acceleration of the block when T is maintained at a constant value, and you plot the results (Figure 1) . The equation for the straight line that best fits your data is a=[0.182m/(Ns2)]T2.842m/s2.
PART A: For this block and surface, what is the coefficient of static friction.
PART B: For this block and surface, what is the coefficient of kinetic friction
Explanation / Answer
T - f = ma = 0
T = f
f_maximum = us.mg = 20
us = 20/9.81m = 2.04 / m
put the value of m and get us.
( you have not provided value of m. )
for T > 20 N
T - f = ma
a = T/m - uk.mg/m
a = (1/m) T - uk.g
comparing it with given equation, a = 0.182 T - 2.842
1/m = 0.182
m = 5.50 kg
so us. = 2.04/ m = 2.04 / 5.50 = 0.37 ........Ans(A)
and uk.g = 2.842
uk =2.842 / 9.81 = 0.30 .......Ans(B)