• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Mechanics 1 P42 2014; Discussion!

Omar Haider

Omar Haider

Messages
120
Reaction score
149
Points
53
For Q3, what if you resolved the 10N force and weight (FIRST) and used that resultant with a triangle of forces to equate the tensions? Also, for the answer you guys got, how can the tension be so small in one wire and so large in another?
 
1

1597.2217

Messages
53
Reaction score
48
Points
28
Oishee Asif
Can you post the workings for questions 5,6 and 7 too?

My answers to 1-4 are at par, not sure about question 5, left Q6b since I ran out of time and wasn't able to solve Q7ii. I think this was a challenging paper, I got over 45 in my past papers whilst practicing.
 
X

xtremeuser12345

Messages
24
Reaction score
40
Points
3
17194 said:
Everyone seems to be having trouble with a simple concept. If I remember correctly the expression for s was s= 3/10 T^5/3. Now according to your logic you had to use the limits 8 and 27, as at 8s the body had already covered 8m. Well then substitute the value of t=8s in this expression. You should end up with 8m, if you are correct. But in reality, you get s=9.6
Click to expand...
That is because of one thing he/she forgot to find the value of c the constant after integrating the s equation which u get from this: 8=9.6+c and u get c=-1.6 not the s(t) equation is 0.3t^5/3-1.6 sub 8 in this equ u still get 8 m.btw,we got c from subbing our co-ord(8,8) in the equation s=0.3t^5/3+c.giving 8=9.6+c,hence c=-1.6,again.this way is the same as her/his way.resulting in a distance of 71.3 m.
 
X

xtremeuser12345

Messages
24
Reaction score
40
Points
3
usama321 said:
71.3 is the correct answer. Oishee has solved it for you by one of the two possible methods, I'll solve it with the other method to assure you.

Disance in the first 8 seconds was 8 m. We would integerate the second equation, with the constant, and equate it to 8, and get the value of C

0.3 t^5/3 + c = 8
0.3 (8)^5/3 + c = 8
c = -1.6

Now, that you have the value of C, just switch in the value of 27
0.3(27)^5/3 -1.6 = 71.3
Click to expand...
exactly i made the same reply just now didnt realise somebody else knew it too and replied.
 
1

17194

Messages
117
Reaction score
60
Points
38
xtremeuser12345 said:
That is because of one thing he/she forgot to find the value of c the constant after integrating the s equation which u get from this: 8=9.6+c and u get c=-1.6 not the s(t) equation is 0.3t^5/3-1.6 sub 8 in this equ u still get 8 m.btw,we got c from subbing our co-ord(8,8) in the equation s=0.3t^5/3+c.giving 8=9.6+c,hence c=-1.6,again.this way is the same as her/his way.resulting in a distance of 71.3 m.
Click to expand...

Okay so let's suppose that the equation you ended up with 's=3/10 T^5/3 - 1.6' is correct for the entire motion of the body, because at t=8 you get the same value of displacement i.e 8m. That means that this equation is applicable to the entire motion. So try it with a different time e.g t=4s. In the linear motion if you substitute the value of t=4s you will end up with a displacement of s=2m (s= 1/2 (0.25) (4^2). Substitute this value into your 'correct' expression of s and you end up with s=1.42m, clearly showing that this is not a universal expression for the entire motion. The motion had to be treated as two separate parts, from t=0 to t=8 and then t=8 to t=27. That is why when the second motion starts at t=8, which is equal to t=0 for motion 2.
 
Oishee Asif

Oishee Asif

Messages
204
Reaction score
455
Points
53
1597.2217 said:
Oishee Asif
Can you post the workings for questions 5,6 and 7 too?

My answers to 1-4 are at par, not sure about question 5, left Q6b since I ran out of time and wasn't able to solve Q7ii. I think this was a challenging paper, I got over 45 in my past papers whilst practicing.
Click to expand...
Sure. Hold on.
 
A

A star

Messages
2,703
Reaction score
3,939
Points
273
seriosuly at this point i really dont carenow cause making them believe wont change my ans and if they are rite then they must be the only few people in karachi to have done this!!
 
Oishee Asif

Oishee Asif

Messages
204
Reaction score
455
Points
53
A star said:
seriosuly at this point i really dont carenow cause making them believe wont change my ans and if they are rite then they must be the only few people in karachi to have done this!!
Click to expand...

And tbh, A star: you, me, and thementor all got the same answers. Along with usama321 and xtremeuser12345.
Thanks for the support. :p
& Mushfiqur Rahman, of course!

And pretty much everyone else in the world, apart from a few people who overthought for an exam. If you had to do that sort of thinking, with such a length paper, and relatively harder than previous years: it would've been worth more marks, instead of the bare 3-4 marks a typical integration question has.
So stfu.
Kthnxbai, end of discussion, case closed.
Anyone wanna go bowling?
 
thementor

thementor

Messages
943
Reaction score
805
Points
103
Oishee Asif said:
And tbh, A star: you, me, and thementor all got the same answers. Along with usama321 and xtremeuser12345.
Thanks for the support. :p
& Mushfiqur Rahman, of course!

And pretty much everyone else in the world, apart from a few people who overthought for an exam. If you had to do that sort of thinking, with such a length paper, and relatively harder than previous years: it would've been worth more marks, instead of the bare 3-4 marks a typical integration question has.
So stfu.
Kthnxbai, end of discussion, case closed.
Anyone wanna go bowling?
Click to expand...
BOWLING !! ME!!
 
You must log in or register to reply here.
Top