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# M1 friction - a particle on a rough horizontal surface watch

1. 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.
2. (Original post by ihatePE)
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.
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.
3. (Original post by 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.
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?
4. (Original post by ihatePE)
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?
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
5. (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
thank you, i can finally sleep tonight

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