All Mechanics DOUBTS HERE!!!

[haris94]

thanx a lot sir

[thecandydoll]

when object A is placed on object B which is placed on the floor(rough horizontal floor)
find co-eff of friction between B and floor.
Mass of a -250
mass of b- 200
A horizontal force of
magnitude PN is applied to B. The boxes remain at rest if P ? 3150 and start to move
if P > 3150.

The coefficient of friction between the two boxes is 0.2. Given that P > 3150 and that no sliding takes
place between the boxes,
(ii) show that the acceleration of the boxes is not greater than 2ms?2,

(iii) find the maximum possible value of P.


How do you go about this kind of sums

[nid404]

when object A is placed on object B which is placed on the floor(rough horizontal floor)
find co-eff of friction between B and floor.
Mass of a -250
mass of b- 200
A horizontal force of
magnitude PN is applied to B. The boxes remain at rest if P ? 3150 and start to move
if P > 3150.

The coefficient of friction between the two boxes is 0.2. Given that P > 3150 and that no sliding takes
place between the boxes,
(ii) show that the acceleration of the boxes is not greater than 2ms?2,

(iii) find the maximum possible value of P.


How do you go about this kind of sums

i) P max= uR
P<= 0.75 x 8000
P<=6000N

ii)F=0.4X4000=1600N

1600>=400a
a<=4m/s^2

Pmax-1600=3200
Pmax=9200 N

[houmeira]

can anyone plz help with this question:

two forces of magnitudes P N and 5 N act on a body. The angle between the two forces is theta and their resultant has magnitude 7N
    
when the direction of the 5 N force is reversed the magnitude of the new resultant is sqrt 19 N
calculate (i) the value of P
             (ii) the value theta

[houmeira]

can anyone plz help with this question:

two forces of magnitudes P N and 5 N act on a body. The nagle between the two forces is theta and their resultant has magnitude 7N
    
when the direction of the 5 N force is reversed the magnitude of the new resultant is sqrt 19 N
calculate (i) the value of P
             (ii) the value theta

 theta is between P N and 5N

[Deadly_king]

can anyone plz help with this question:

two forces of magnitudes P N and 5 N act on a body. The angle between the two forces is theta and their resultant has magnitude 7N
    
when the direction of the 5 N force is reversed the magnitude of the new resultant is sqrt 19 N
calculate (i) the value of P
             (ii) the value theta

I'll take theta as A
Using cosine rule :
7² = 5² + P² - 2(5)(P)cosA
49 = 25 + P² - 10PcosA
24 = P² - 10PcosA
That is the first equation.

Again use the cosine rule
19 = 25 +P² -10Pcos(180-A)
-6 = P² - 10Pcos(180-A)

This is the second equation. Now you just need to solve simultaneously

[houmeira]

yeah thanks i've tried itbefore and it's the simultaneous eqtn..i'm getting trouble to solve:S
need some help to solve it><

[houmeira]

yeah thanks i've tried itbefore and it's the simultaneous eqtn..i'm getting trouble to solve:S
need some help to solve it><

yay i got the answer!!#
thanks deadly king:P

[Deadly_king]

yay i got the answer!!#
thanks deadly king:P

Ok then

you welcome

[astarmathsandphysics]

elastic question someone asked me on skype

A light elastic string has natural length 2.5m and modulus elasticity 15 N. A particle P of mass 0.5kg is attached to the string at the point K where K divides the unstretched string in the ratio 2:3. The ends of the string are then attached to the points A and B which are 5m apart on a smooth horizontal surface. The particle is then pulled aside and held at rest in contact with the surface at the point C where AC = 3m and ACB is a straight line. The particle is then released from rest.
a) show that P moves with simple harmonic motion of period pi/5 root2
b) find the amplitude of the motion

[thecandydoll]

CIE
MAy june 2010.
paper 4,mechanics
Variant 43
Question 4.

We have to find the co-eff of friction of b.
We know Tension.
calculate for above subquestion.
it says the B moves up,so does this mean it accelerate up?
There fore T and a must be in the same direction?
Friction in the opposite direction?
I dont get it.

Please clear this for me.

[nid404]

2 objects joined together by an inextensible string; the string will have an even tension and particles will have the same acceleration.

So whether the particle is moving up or down, they both have the same acceleration.

I've drawn the free body diagram, hope it helps.

attached.

[thecandydoll]

2009 oct november
mechanics cie
paper 41
Q4!

[nid404]

I hope you understood the post above :/

Nov 09 Q4 --> https://studentforums.biz/math-146/mechanics-question/15/

[thecandydoll]

Thank youuu
And one more.
CIE.
MECHANICS.
PAPER 42. MAY/JUNE 2010.
Q6 (ii)
In the markscheme it says

0.2a2 = –0.06g

how do they get the -0.06