An object with a mass of #2 kg# is on a surface with a kinetic friction coefficient of # 9 #. How much force is necessary to accelerate the object horizontally at #6# #ms^-2#?

1 Answer
Jan 25, 2016

Answer:

If the object were on a frictionless surface the force required would be #12# #N#, but including the frictional force it is #188.4# #N#, but see the explanation: this is a silly answer because there is a problem with the question.

Explanation:

This is a very badly written question: the friction coefficient should have values between 0 and 1. Very rarely it can have values greater than one, and perhaps as high as 2, but 9 is a ridiculous and non-physical number. Are you sure it wasn't 0.9 and you missed something when writing down the question?

First we can calculate the required force due to the object's inertia:

#F = ma = 2*6 = 12# #N#

This is the force we'd need on a frictionless surface.

To calculate the frictional force, use:

#F_f = muF_N# where #F_N# is the normal force acting - in this case the weight force of the object, #mg = 2*9.8 = 19.6# #N#.

#F_f = muF_N = 9*19.6 = 176.4# #N#

To find the total force required we would add this to the #12# #N# above, but this is a silly number...