M1 - Monday 9:00am -the key to success-

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TheWolf

can you name one either from the heinemann edexcel m1 book or from a past paper? because i dont think ive seen one :confused:

Sorry, I don't have my M1 textbook on me at the moment. Check the few last questions on the vectors section there's probably one there.

Reply 21

TheWolf

gd gd got the right answer :cool:

Reply 22

john !!

That's probably the hardest element of M1. Oh, I forgot one other:

When the string snaps and you have to find the displacement. You have the initial acceleration, and draw another diagram to work out the second acceleration without the tension force. Work out the first displacement, and the final velocity when the string snaps, put this equal to the initial velocity with the new acceleration, and use Newton's equations to find the total displacement/time. This is usually at the end of a question for an extra 3/4 marks.

Reply 23

stanny

mik1a

This means their displacements from the origin are (9 - 5t)i + (7 -2t)j and (7t)i + (3t - 11)j respectively. Their distance is the difference between these, so subtract the second from the first to get:

s = (9 - 12t)i + (16 - 5t)j

Take the magnitude using pythagoras:

|s|^2 = (9 - 12t)^2 + (16 - 5t)^2
|s|^2 = 144t^2 -216t + 81 + 25t^2 -160t + 256
|s|^2 = 169t^2 - 376t + 337

Differentiate to find the change in |s|^2 by the change in t:

d|s|^2/dt = 338t -376

Put equal to 0 to find the turning points and solve for t:

0 = 338t -376
338t = 376
t = 1.11 s

this is wt i got... different from mik1a

A: s=(9-5j)i+(7-2t)
B: s=7i+(-11+3t)j
B-A: s= (-2i+5t)i+(-17+5t)j
s^2=50t^2-190t-285
ds/dt=100t-190
100t-190=0
t=1.9

further prove that this is the minimum point:
d^2s/dt^2=100
+ve proves minimum.

bye i sleep.

Reply 24

john !!

stanny

A: s=(9-5j)i+(7-2t)

I tried to check it, but this was a bit confusing. A: s=(9-5j)i+(7-2t)? :tongue:

good stuff there

etomac

good stuff there

Thanks.

Reply 27

TheWolf

ok ive finished m1 revision - can people post here some v.hard questions that they cant do or is a difficult question or something - so i can (1) help and (2) more practice for me? ta

Reply 28

adk

TheWolf

ok ive finished m1 revision - can people post here some v.hard questions that they cant do or is a difficult question or something - so i can (1) help and (2) more practice for me? ta

Yeah good question.

Bring on the hardest questions!!

Reply 29

TheWolf

ok:heres a gd question:

At 6:00am a cargo ship has position vector (7i + 56j)km relative to a fixed origin O on the coast and moves with constant velocity (9i - 6j) kmh/

A ferry sals from O at 6:00am and moves with constant velocity (12i + 18j)kmh. The unit vectors i and j are directed due east and due north respectively.

(a) Show that the position vector of the cargo ship t hours after 6:00am is given by :

[(7 + 9t)i + (56 - 6t)j]km

and find the position vector of the ferry in terms of t

(b) Show that if both vessels maintain their course and speed, they will collide and find the time and position vector at which this occurs.

At 8:00am the captain of the ferry realises that a collision is imminent and changes course so that the ferry now has velocity (21i + 6j)jmh

(c) Find the distance between the two ships at the time when they would have collided

Reply 30

stanny

mik1a

I tried to check it, but this was a bit confusing. A: s=(9-5j)i+(7-2t)? :tongue:

dude the ans is right... the previous parts i jus typed wrong...

A: s=(9-5t)i+(7-2t)j

Reply 31

stanny

hey i hav a question here.

when u give sth in terms of sth, do u like... eg. vectors

express p in terms of t,
do i write sth like:
(8i + j) + (6i +7j)t

or expand this so u get:
(8 + 6t)i + (1 + 7t)j ???

Reply 32

Lithium

I was woundering if i could use " laws" not mentioned in the syll. to solve questions? e.g. When you are given info about two bodies colliding " Post and pile driver" which penetrate the ground each time its hammerd, and the give you thier masses and velocities, and tell you how far it goes into the ground, then asks for The resistave force!

could i use:

Force * Distance = Change in Kinetic Energy i.e.

F.d= 0.5 m v^2 ?

Reply 33

stanny

TheWolf

a)
s=(7i+56j)+(9i+6j)t
then expand... cant b bothered to type
s=12it+18jt

b) t=2/1/3 hours
so 6:00 + 140 min = 8:20

c)
ferry
s=(12i+18j)2
=(24i+36j)km
At 8:20,
s=(31i+38j)
cargo:
(28i+42j) at 8:20
cargo - ferry=(3i-4j)km
pythagoras get 5km.

Reply 34

john !!