All Mechanics DOUBTS HERE!!!

[nid404]

A large crate of mass 40kg lies at rest on rough horizontal ground. One end of the rope is attached to the crate and the rope makes an angle of 30 with ground as shown in the diagram. The tension of the rope is 150N and the crate is on the of moving along the plane.
By modelling the crate as a particle,
(a) Find the value of [mue], the cofficient of frction between the crate and the ground.
The rope remains at 30 degree to the ground but the tension init is increased to 200N.
(b) Find the acceleration of the crate.
 

a) u= F/R

F=150cos30
R=400-150sin30

u=130/325
  =0.4

b) horizontal force=Tcos30=200cos30=173.3N
       173-F(uR)=40a
       173-130=40a
       a=3.4m/s2

[Saladin]

here u go.

[Khey [Rainbow]]

Thanks to "nid404" and "the mysterious dude"
but both of u have differnt answers so m confused bout who's answer is right..but its alryt i will ask my teacher
once again Thanks alot

[nid404]

lol...ohk

i dunno....I think R= mg-150sin30

[Saladin]

Mine is, I did it the Edexcel method, and if it was 3.4 ms-2, that would have been too high a speed, considering that at 150, it would not move.

[MasterMath]

I can help , give me a sec to look at the question!

[MasterMath]

CONFRIMED , I got the same answers as The Mysterious Dude

[halosh92]

two particles P and Q of masses 1kg and 2kg respectively are hanging from the ends of  alight inextensible string which passes over  a smooth fixed pulley. the system is released from rest with both particles a distance 1.5m above a  floor. when the masses have been moving fir 0.5 s the string breaks. find the furthur time that elapses  before P hits the floor
 

can someone solve this in more details please??

[Sue T]

jan 2007:
can ny1 solve the last question 7(f)?

[halosh92]

a particle A of mass "m" which can move on the rough surface of an inclined plane at an angle X to the horizontal.
where X=arcsin 0.6
a second particle B of mass "2m" hangs freely attached to a light inextensible string which passes over a smooth pulley fixed at P. the other end of the string is attached at A . the coefficient of friction between A and the plane is 1/4.
B is initially hanging 1m above the ground and A is 2m from the pulley. when the system is released from rest with the string taut A moves up the plane
a) find the initial acceleration of A
b) calculate the total distance moved by A before it first comes to rest.

[cashem'up]

Thanks to "nid404" and "the mysterious dude"
but both of u have differnt answers so m confused bout who's answer is right..but its alryt i will ask my teacher
once again Thanks alot

no i am pretty sure nid404 is correct because to find the the Normal Contact u have to find the resulting vertical downward force that box exerts on ground and then the normal will be same as that.
If u also think logically when ur pulling something at such an angle u will be lifting some of the weight off........ dont take this literally but logically so less force will be exerted on the ground...... u get wat i am saying

[cashem'up]

two particles P and Q of masses 1kg and 2kg respectively are hanging from the ends of  alight inextensible string which passes over  a smooth fixed pulley. the system is released from rest with both particles a distance 1.5m above a  floor. when the masses have been moving fir 0.5 s the string breaks. find the furthur time that elapses  before P hits the floor
 

hey halosh is the answer possibly 1.01 seconds

[cashem'up]

a particle A of mass "m" which can move on the rough surface of an inclined plane at an angle X to the horizontal.
where X=arcsin 0.6
a second particle B of mass "2m" hangs freely attached to a light inextensible string which passes over a smooth pulley fixed at P. the other end of the string is attached at A . the coefficient of friction between A and the plane is 1/4.
B is initially hanging 1m above the ground and A is 2m from the pulley. when the system is released from rest with the string taut A moves up the plane
a) find the initial acceleration of A
b) calculate the total distance moved by A before it first comes to rest.

answer to (a) should be 4m/s2
and to (b) 1.99 m

if iam correct i will explain , dont want to confuse you with wrong answrs.......

[halosh92]

answer to (a) should be 4m/s2
and to (b) 1.99 m

if iam correct i will explain , dont want to confuse you with wrong answrs.......

this is the exact answer:
3.92 m/s
1.5 m
thankyou 

[immortal]

here u go.

using this method i got a different ans.

u=0.3997
200cos30-(u*(40g-200sin30)=40a
a=1.33
If i replace da red wit 150sin30, i get ur ans.