An object with a mass of #7 kg# is on a surface with a kinetic friction coefficient of # 7 #. How much force is necessary to accelerate the object horizontally at #28 m/s^2#?

1 Answer
Mar 26, 2016

Answer:

I found: #676N#

Explanation:

Consider the diagram:
enter image source here
We can use Newton's Second Law: #SigmavecF=mveca#
on the #x# and #y# axis as:
#F-f=ma#
#N-W=0#
where:
#N# is the normal reaction;
#W# is the weight (#=mg#);
#f=mu_kN# is kinetic friction;
#a=28m/s^2# is acceleration.
So we get from the second that:
#N=W=mg#
into the first:
#F-mu_k*mg=ma#
#F-(7*7*9.8)=7*28#
so:
#F=196+480.2=676.2~~676N#