You are Here: Home >< Maths

# Urgent Ocr Mechanics 1 Help Needed Please (again) !!! watch

1. HEY ANOTHER PROBLEM HERE, MAJOR REP GIVEN FOR ANY HELPERS !

7)
TWO PARTICLES A AND B, OF MASSES O.5kg and M kg RESPECTIVELY, ARE JOINED BY A LIGHT INEXTENSIBLE STRING.

PARTICLE A RESTS ON A BOARD WHICH IS FIXED AT 10 DEGREES TO THE HORIZONTAL. THE COEFFICIENT OF FRICTION BETWEEN A AND THE BOARD IS 0.15, THE STRING IS PARALLEL TO A LINE OF GREATEST SLOPE OF THE BOARD AND PASSES OVER A SMALL SMOOTH PULLEY AT THE TOP OF THE BOARD. PARTICLE B HANGS VERTICALLY BELOW THE PULLEY.

THE SYSTEM IS IN EQUILIBRIUM.

a) Given that A is on the point of sliding up the plane, show that m=0.161, correct to 3dp

b) Given instead that A is on the point of sliding down the plane, show that m = 0.013, correct to 3dp

ANY HELP WILL BE MUCH APPRECIATED AND I WILL LEAVE GOOD REP, PLEASE TRY AND HELP ME OUT !
2. If you resolve on A to get the normal contact force:

R=4.9cos10=4.83N

Then you can work out Friction Flim=Ru=4.83*0.15=0.724N

Then resolve on A: T-0.724-4.9sin10=0 T=1.57

so then you can resolve on B : 1.57-mg=0 m=0.161kg

hope that makes sense!

T = tension btw!
3. a)
draw a force diagram. i cant be bothered to upload one
R = 0.5gcos10
F = 0.15*0.5gcos10
friction acts down slope

in equilibrium, acceleration is 0
T = tension in string
force up slope = force down slope
Mg = T = F + 0.5gsin10
M = (0.5gsin10 + 0.15*0.5cos10)/g
M = 0.161kg

b)
friction acts up slope.
F = 0.15*0.5gcos10
force down slope = force up slope
0.5gsin10 = F + Mg
(0.5gsin10 - 0.15* 0.5gcos10)/g = M
M = 0.0130kg
4. Oh and good luck with the exam tomorrow! I've got M1 and C3 tomorrow too!
5. (Original post by fabz)
Oh and good luck with the exam tomorrow! I've got M1 and C3 tomorrow too!
me too gl
6. (Original post by Undry1)
me too gl
How do you think you'll do? I've done a few practice papers today and my marks ranged from 89% to 49% for C3!
7. i should be fine i think. done plenty of past papers. unless there's a HARD question i should do ok . (famous last words)
8. Thanks a lot guys, credits on its way as soon as possible

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: June 15, 2005
The home of Results and Clearing

### 2,846

people online now

### 1,567,000

students helped last year
Today on TSR

### Got into uni yesterday?

Come start a Freshers blog and win pizza!

### University open days

1. London Metropolitan University
Sat, 18 Aug '18
2. Edge Hill University
Sat, 18 Aug '18
3. Bournemouth University
Sat, 18 Aug '18
Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams