M1 - Help thread

M1 is a brilliant module, although it can be quite hard if you don't get your head around the key concepts.

Tips - check, double check, triple check, and check again your workings and diagrams. A "sin" instead of a "cos", the omittal of a force or a simple calculator error can give you the completely wrong answer.

Reply 2

if this is a help thread can someone help me with the triangle questions in m1 where we have to work out resultants and friction and tension etc, i really can't understand it from the book and my teacher is going too fast, any worked step by step example would be great!

Reply 3

specify the q u have in mind please - ill try help if i can.....

Reply 4

Archibald246

13

I hate mechanics.... I did M1 last year and got a D in the module, but then resitted it this jan and got an A somehow. I think you just have to do enough past papers and example questions until you crack it. It will suddenly quick (although possibly a bit too late for me, but it worked out in the end!)

Reply 5

lol this jan I knew i had done badly and did :frown:

Everyone finds some topics easy and others harder

Reply 6

gj3

if this is a help thread can someone help me with the triangle questions in m1 where we have to work out resultants and friction and tension etc, i really can't understand it from the book and my teacher is going too fast, any worked step by step example would be great!

If you give me an example of the kind of question you have in mind, I'd be happy to help :smile:

Reply 7

thanks guys

Heres one:

A parcel of weight 10 N lies on a rough plane inclined at an angle of 30* to the horizontal. A horizontal force of magnitude P newton acts on a parcel. The parcel is in equilibrium and on the point of slipping up the plane. The normal reaction of the plance on the parcel is 18 N. The coefficent of friction between the parcel and the plane if u.

Find the value of P?

Find the value of u?

The horizontal force is removed determine whether or not the parcel moves?

Reply 8

gj3

thanks guys

Heres one:

A parcel of weight 10 N lies on a rough plane inclined at an angle of 30* to the horizontal. A horizontal force of magnitude P newton acts on a parcel. The parcel is in equilibrium and on the point of slipping up the plane. The normal reaction of the plance on the parcel is 18 N. The coefficent of friction between the parcel and the plane if u.

Find the value of P?

Find the value of u?

The horizontal force is removed determine whether or not the parcel moves?

Draw a diagram, labelling the horizontal force, the weight, the normal reaction and the frictional force (which will be acting down the plane, as the parcel is about to slip up the plane). Then you can resolve the forces and remember that the resultant force is going to be in 0, as the parcel is in equilibrium.

For the second part, remember F=uR?

The third part, draw a separate diagram like the first, except without the horizontal force (and the friction will be acting in the other direction).

Reply 9

could you explain the above first part further, what i mean is that i don't have a great understanding of how to exactly put forces into resultants etc.

Reply 10

parcel forces diagram.jpg38.4KB

I've drawn a little diagram for you, detailing all of the forces acting on the parcel, which is attached.

If I now told to you resolve perpendicular to the plane, would you know what to do?

EDIT: forgot to include on my diagram that R = 18 N.

Reply 11

by my poor mathematical calculations, I get:

1.....18-Psin30-10cos30=0
therefore P=18.67949 or so

2.....Pcos30-F-10sin30=0
therefore F=11.1769

3.....F=uR
so 11.1769=18u
therefore u=0.621 (3sf)

Reply 12

A small ring if mass 0.25 is threaded on a fixed rough horizontal rod. The ring is pulled upwards by a light string which makes an angle 40 with the horizontal. The string and the rod are in the same vertical plane. The tension in the string is 1.2n and the cof is U. Given that the ring is in limiting equilibrium find the normal reaction? And find U?

I get the first as 2.38N?

and the second as 0.38

Reply 13

again do the same as i did.... I'm a bit busy right now but I'll see if you're right a bit later on.

Reply 14

so my answer is wrong?

Reply 15

M.A.H

sohanshah

by my poor mathematical calculations, I get:

1.....18-Psin30-10cos30=0
therefore P=18.67949 or so

2.....Pcos30-F-10sin30=0
therefore F=11.1769

3.....F=uR
so 11.1769=18u
therefore u=0.621 (3sf)

I got 1) = 18+Psin30-10sin60=0 I get the same asnwer but negative :confused:

Reply 16

M.A.H

I got 1) = 18+Psin30-10sin60=0 I get the same asnwer but negative :confused:

U have done 18+ instead of 18-
Look at your own diagram... the 2 forces are going in opposite directions so its a minus

or u cud do -18+ etc and switch all the signs round

Reply 17

I believe you are wrong gj3

I get R=1.67865

and u=0.548

Reply 18

and I arrive at that by doing....

1.....F=1.2cos40
F=0.91925

2.....R+1.2sin40=(0.25g) where g is gravity i.e 9.8 on earth
R=1.67865

3.....F=uR
u=0.5467 etc...

Reply 19