Edexcel M1 ex2D Question 11b

OP

yeah they do start at 0

Reply 4

OP

Original post by TheMagicMan

Work out at what time C passes M. Then work out the displacement of either C or M at this time: this will be the displacement of the pedestrian

i tried but I'm still getting the wrong answer, is t= 16?

Reply 5

OP

Original post by TheMagicMan

I get t=20 I think.

To do it with working: write down an expression for the displacements of C and M in terms of t, then equate these for t.

do you use the formula S=ut-1/2at^2 for both C and M and then equate them in terms of t

Reply 6

OP

i got t=20 but when i try to find the displacement I got 480, the answer is 720, i don't get where I when wrong??

Reply 7

OP

Original post by TheMagicMan

I get the displacement as 300 at t=20.. are you sure you've got the whole question written down?

yeah I'm sure I have

Reply 8

TheMagicMan

15

Original post by jonehim

yeah I'm sure I have

My mental maths failed completely I just realised.

The book is right. Try to do it by equating the suvats and working out a value for t

Spoiler

Reply 9

OP

for M
u=0
v=24
a=3

for C
u=0
v=24
a=1.5

Reply 10

I got s=720

But then again I got t=34

Reply 11

OP

I'm trying to get t=34 but i can't seem to get it

Reply 12

TheMagicMan

15

Original post by TenOfThem

I got s=720

But then again I got t=34

You are right. I realised that I did something really stupid in my mental maths which didn't help at all

Reply 13

For M

s = 96 + 24(t-8)

Do you know why and if so can you make a similar s for C

OP

how do you get t=34?

OP

Original post by TenOfThem

For M

s = 96 + 24(t-8)

Do you know why and if so can you make a similar s for C

i know, but where did you get your 96 from??

Reply 16

\frac{1}{2}* 3 * 8^2

Reply 17

OP

how do you get the equation for C?

Reply 18