An object with a mass of 2 kg2kg is on a surface with a kinetic friction coefficient of 9 9. How much force is necessary to accelerate the object horizontally at 66 ms^-2ms2?

1 Answer
Jan 25, 2016

If the object were on a frictionless surface the force required would be 1212 NN, but including the frictional force it is 188.4188.4 NN, 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 = 12F=ma=26=12 NN

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

To calculate the frictional force, use:

F_f = muF_NFf=μFN where F_NFN is the normal force acting - in this case the weight force of the object, mg = 2*9.8 = 19.6mg=29.8=19.6 NN.

F_f = muF_N = 9*19.6 = 176.4Ff=μFN=919.6=176.4 NN

To find the total force required we would add this to the 1212 NN above, but this is a silly number...