m1 hard QUESTION

particles A and B of masses 0.1kg and 0.32kg respectively are attached to the ends of a light inextensible string. the string passes over a smooth fixed pulley at the top of the rough plane which is inclined at an angle alpha to the horizontal. it is given that sin alpha is 0.6 and cos alpha is 0.8. particle A is held in contact with the plane and particle B hangs vertically below the pulley.the coefficient of friction between A and the plane is 1/4. particle A is released and the system starts to move. find:

i)the acceleration of A (7 marks)

ii)the distance travelled by A when the speed has reached 2.8m/s(assuming A has not reached the pulley) (2 marks)

iii) when the speed is 2.8m/s the string breaks. particle A continues to move up the plane without reaching the pulley. find the distance between the initial position of A and the highest point reached by A

Reply 1

goku999

Briefly

Find the angle alpha by sin-1(o.6) or cos-1(0.8) same answer

You need to resolve the forces perpendicular to the plane to get the reaction force.

Then do F=Mr to get u the friction.

Friction acts up the plane
Then solve the forces parallel to the plane using F=ma

Find acceleration as u know what friction is.

Reply 2

hellooooo

thats kinda what i tried but i got:
i)17.76
ii)0.22 m
iii)0.62m

just wonderin if theyre correct? (cos the answer to i sounds a bit wrong lol

Reply 3

Master Gee

I hope you don't mind but I got rid of me saying that T = 0.32g as I couldn't stand the shame :frown:

Reply 4

Fermat

T is the tension in the string.

"T - Fr - 0.1g.sin@" is the accelerating force on mass A = Ma*accln
"0.32g - T" is the accelerating force on mass B = Mb*accln

where accln is the common acceleration of both masses

Reply 5

Fermat

and if you add these two eqns, you get,

0.32g - Fr - 0.1gsin@ = (Ma + Mb)*accln

Reply 6

hellooooo

so whats the answer for part i) then? i got 17.76 without sayin t=0.32g

Reply 7

Master Gee

I'm actually being clinically instituted for retardedness, i apologise.
I'm doing Fmaths would you believe!!!!
Right, I'm off to rent out a hotel room to have a cry for the night.