All Mechanics DOUBTS HERE!!!

[elemis]

Doing it now.

[elemis]

s = ut + 0.5at²

s = 20*12 + 0.5*-2.5*12²

s = 60m

--------------------------------------------

I cant answer the second part since you must have left some information out or maybe the question is wrong.

[**RoRo**]

s = ut + 0.5at²

s = 20*12 + 0.5*-2.5*12²

s = 60m

--------------------------------------------

I cant answer the second part since you must have left some information out or maybe the question is wrong.

Thank you!

Nope, the question is complete from the textbook.

According to the CD that I have, this is the working of the answer.

The particle will turn round when v=0.

a =?2.5, u=20, v=0, s=?

v² =u²+2a?s

0² =20²?5s

?s=80
 
The total distance P travels is (80+20)m=100m.

& the photo attached is the photo that they have shown.

It's alright, I figured it out now, I copied a wrong number into my calculator and hence my entire working was wrong! -.-'

Thank you! 

[elemis]

True, that skipped my mind. Glad you figured it out.

[**RoRo**]

Okay, a few [probably stupid and silly] questions related to the presentation of answers, but I guess they do matter when answering a paper!

1. How many s.f. are we supposed to leave our answers to? 2 or 3?

2. For questions on bearings, do we leave our angles to only 1 d.p.?

3. If a bearing is 42.5, do we leave the answer as 42.5 or 042.5? [since bearings are supposed to consist of 3 digits]

4. If an answer to a question is a long decimal, for example, an answer is 0.714285714 on the calculator, do I leave the answer as 0.71 or (5/7)?

[elemis]

Answers to 3 s.f. unless told otherwise.

Angles to 1 d.p.

Giving it as either will get the mark, however, to be safe stick to 042.5

State the answer exactly i.e. in fractions or surds whenever possible.

[**RoRo**]

Okie! Thanks a lot! 

[elemis]

Okie! Thanks a lot! 

Good luck

When are you doing your M1 exam ? CIE or Edexcel ?

[**RoRo**]

Thank you!

I'm doing Edexcel, in the May/June 2011 session.

But I've got my first term school exams in a week, so yea, I'm preparing for them now!

What about you?

[elemis]

Thank you!

I'm doing Edexcel, in the May/June 2011 session.

But I've got my first term school exams in a week, so yea, I'm preparing for them now!

What about you?

I'm doing M1 this coming January.

[**RoRo**]

Good luck!! (Y)

My school doesn't allow us to take any exams in November [for CIE] and January [for Edexcel], just the May/June session! :/

[mdwael]

A particle P is moving on the x-axis with constant deceleration of 4 (ms^-2). At time t= 0, P passes through the origin O with velocity 14 (ms-1) in the positive direction. The point A lies on the axis and OA = 22.5 m.
a) Find the difference between the times when P passes through A. (ans 2 sec)
b) Find the total distance travelled by P during the interval between these times. (ans 4m)

I got the first part as 2 sec which is correct, the second part is 4m but I dont understand how do you reach this answer?

Thanks in advance

[astarmathsandphysics]

s=0
u=
v=
a=-4
t=2
by symmetry v=-u
a=(v-u)/t
-4=2v/2
v=-4
s=
u=4
v=0
a=-4
t=1
s=ut+1/2at^2=4*1+1/2*-4*1^2=2
2m to stop and 2m back=4m

[astarmathsandphysics]

Q)Perry left school driving towards the lake one hour before jaidee.
jaidee drove in the opposite direction going 6mph slower then perry for one hour after which time they
were 174 min apart. What was perry's speed.
I assume you mean 174 miles apart.
Perry's speed is v. After t hours Perry's distance from start point is vt.
Jaidee's distqance from start point is (t-1)(v-6)
vt+ (t-1)(v-6)=174
t=2 cos jaidee drove for 1 hour, 1 hour less than Perry.
2v+v-6=174
v=30

[S.M.A.T]

I am stuck on part b) of this question,I thought the answer is 0.5m but the book's answer is 0.4m

someone please help.

thanks in advance