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M1 friction - a particle on a rough horizontal surface

a particle of mass 3kg moves in straight line on rough surface. coefficient of friction between surface and particle is 6/49

a) find the frictional force and show that the deceleration of particle is 1.2ms^-2

i found that frictional force is 3.6N, correct me if im wrong

but then no idea how to show the deceleration, i figured i'd use f=ma

so p-3.6=3a

there's 2 letters in there, and im stuck.

Reply 1

SherlockHolmes

3.6N is correct.

Now you want to resolve horizontally (in the direction of motion) using F=ma.

The resultant force in the direction of motion is -F, which is -3.6 i.e. there is only a friction force present. Set this equal to ma and rearrange for a.

Reply 2

TSR George

Original post by SherlockHolmes

that always get to me, i always automatically think there should be 2 force that should go in the F in f=ma.

so:

-3.6=3a?

Reply 3

SherlockHolmes

Yes you should always draw a diagram and label all of the forces acting on the particle first before starting the question.

Yes that's right. Rearranging gives a = -1.2 :smile:

Reply 4

TSR George

Original post by SherlockHolmes

Yes you should always draw a diagram and label all of the forces acting on the particle first before starting the question.

Yes that's right. Rearranging gives a = -1.2 :smile:

thank you, i can finally sleep tonight