# Another Lovely M1 Question - yes you love it!

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The brakes of a train can produce a retartdation of 1.7ms-2. If the train is travelling at 100kmh-1 and applies its brakes, what distance does it travel before stopping? If the driver applies the brakes 15m too late to stop at a station with what speed is the train travelling when it passes through that station?

I got hte first part correct:

U= 100kmh-1

after converted

27.8ms -1

a= -1.7ms-2

Equte them variables into the formulae to get:

V^2=U^2+2as

0=27.8^2+2(-1.7)s

s=772.84/3.4 = 227m

How do you do part B? Thanks!

I got hte first part correct:

U= 100kmh-1

after converted

27.8ms -1

a= -1.7ms-2

Equte them variables into the formulae to get:

V^2=U^2+2as

0=27.8^2+2(-1.7)s

s=772.84/3.4 = 227m

How do you do part B? Thanks!

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#2

The train needs 227 m to stop, So it puts the brakes on 15m late which means it will travel 15m past the station. What you have to find is the speed of the train when it reaches the station which will be when it has travelled 227 - 15 = 212 m.

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#3

if what fermat says is right, this should be:

v=?

u=100km/h

t=15

a=-1.7ms-2

v=u+at

=100000+(15*60*-1.7)

=98.47kms-1 i think im trying and i could be wrong

v=?

u=100km/h

t=15

a=-1.7ms-2

v=u+at

=100000+(15*60*-1.7)

=98.47kms-1 i think im trying and i could be wrong

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(Original post by

if what fermat says is right, this should be:

v=?

u=100km/h

t=15

a=-1.7ms-2

v=u+at

=100000+(15*60*-1.7)

=98.47kms-1 i think im trying and i could be wrong

**magiccarpet**)if what fermat says is right, this should be:

v=?

u=100km/h

t=15

a=-1.7ms-2

v=u+at

=100000+(15*60*-1.7)

=98.47kms-1 i think im trying and i could be wrong

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#5

crap im in the library gotta go soon cos its closing. when do you need to know for? cos i really wana know how to do it, i can do it tonite and send u the ansewr tomoro bout 10am?

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(Original post by

crap im in the library gotta go soon cos its closing. when do you need to know for? cos i really wana know how to do it, i can do it tonite and send u the ansewr tomoro bout 10am?

**magiccarpet**)crap im in the library gotta go soon cos its closing. when do you need to know for? cos i really wana know how to do it, i can do it tonite and send u the ansewr tomoro bout 10am?

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#7

actually what fermat says is wrong. just quickly, the 15 mins too late to stop at the station means 15 mins of the total stopping time not 15 mins=15metres at 100km. wotk out total stopping time using u=0 v=100 a=-1.7 then subtract 15 mins from it should then work it out using t=your answer,u=? v=100 a=1.7. i got 10 mins gonna try now but im sure this is how

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(Original post by

actually what fermat says is wrong. just quickly, the 15 mins too late to stop at the station means 15 mins of the total stopping time not 15 mins=15metres at 100km. wotk out total stopping time using u=0 v=100 a=-1.7 then subtract 15 mins from it should then work it out using t=your answer,u=? v=100 a=1.7. i got 10 mins gonna try now but im sure this is how

**magiccarpet**)actually what fermat says is wrong. just quickly, the 15 mins too late to stop at the station means 15 mins of the total stopping time not 15 mins=15metres at 100km. wotk out total stopping time using u=0 v=100 a=-1.7 then subtract 15 mins from it should then work it out using t=your answer,u=? v=100 a=1.7. i got 10 mins gonna try now but im sure this is how

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#9

ok well im off now. put your t into v=u+at with u=? v=100 a=1.7

i think this is how but i cant do it now cos i gotta go and the library opens at 10am 2mo so if i can do it i send it to you then via pm

good night!

i think this is how but i cant do it now cos i gotta go and the library opens at 10am 2mo so if i can do it i send it to you then via pm

good night!

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(Original post by

ok well im off now. put your t into v=u+at with u=? v=100 a=1.7

i think this is how but i cant do it now cos i gotta go and the library opens at 10am 2mo so if i can do it i send it to you then via pm

good night!

**magiccarpet**)ok well im off now. put your t into v=u+at with u=? v=100 a=1.7

i think this is how but i cant do it now cos i gotta go and the library opens at 10am 2mo so if i can do it i send it to you then via pm

good night!

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#12

(Original post by

I can get 7.21m/s!

v^2=u^2+2as

v we want to find

u=100km/h

a=-1.7

s=227-15=212

**juno_the**)I can get 7.21m/s!

v^2=u^2+2as

v we want to find

u=100km/h

a=-1.7

s=227-15=212

That's the right formula as well.

v² = u² -2ds

v = ?

u = 100km/h = 27.78 m/s

d = 1.7 m/s²

s = 227 - 15 = 212 m

v² = (27.78)² - 2*1.7*212

v² = 771.73 - 720.8

v² = 50.93

v = 7.136

v = 7.14 m/s

=========

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#13

(Original post by

The brakes of a train can produce a retartdation of 1.7ms-2.

1.) If the train is travelling at 100 kmh-1 and applies its brakes, what distance does it travel before stopping?

2.) If the driver applies the brakes 15m too late to stop at a station, with what speed is the train travelling when it passes through that station?

**DOJO**)The brakes of a train can produce a retartdation of 1.7ms-2.

1.) If the train is travelling at 100 kmh-1 and applies its brakes, what distance does it travel before stopping?

2.) If the driver applies the brakes 15m too late to stop at a station, with what speed is the train travelling when it passes through that station?

a = -1.7, u = (100 * 10^3)/(60^2) = 250/9 ms^-1, v = 0.

v^2 = u^2 + 2as

---> 0 = (250/9)^2 - 2(1.7)s

---> 3.4s = (250^2)/81

---> s = (250^2)/(81 * 3.4)

--->

**Distance Travelled (To Stop) = 226.9 m**

2.) From passing through the station to stopping:

a = -1.7, s = 15, v = 0.

v^2 = u^2 + 2as

---> 0 = u^2 - 2(1.7)(15)

---> u^2 = 51

--->

**Speed (Passing Through Station) = 7.14 ms^-1**

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(Original post by

1.) From applying the brakes to stopping:

a = -1.7, u = (100 * 10^3)/(60^2) = 250/9 ms^-1, v = 0.

v^2 = u^2 + 2as

---> 0 = (250/9)^2 - 2(1.7)s

---> 3.42s = (250^2)/81

---> s = (250^2)/(81 * 3.42)

--->

2.) From passing through the station to stopping:

a = -1.7, s = 15, v = 0.

v^2 = u^2 + 2as

---> 0 = u^2 - 2(1.7)(15)

---> u^2 = 51

--->

**Nima**)1.) From applying the brakes to stopping:

a = -1.7, u = (100 * 10^3)/(60^2) = 250/9 ms^-1, v = 0.

v^2 = u^2 + 2as

---> 0 = (250/9)^2 - 2(1.7)s

---> 3.42s = (250^2)/81

---> s = (250^2)/(81 * 3.42)

--->

**Distance Travelled (To Stop) = 225.6 m**2.) From passing through the station to stopping:

a = -1.7, s = 15, v = 0.

v^2 = u^2 + 2as

---> 0 = u^2 - 2(1.7)(15)

---> u^2 = 51

--->

**Speed (Passing Through Station) = 7.14 ms^-1**
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(Original post by

You're wrong, the first part is 225.6 m.

You rounded quantities during the question, included initial velocity, and thus got a slightly less accurate answer.

I used 250/9 ms^-1, and went from there, which was more accurate.

**Nima**)You're wrong, the first part is 225.6 m.

You rounded quantities during the question, included initial velocity, and thus got a slightly less accurate answer.

I used 250/9 ms^-1, and went from there, which was more accurate.

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#16

(Original post by

---> 0 = (250/9)^2 - 2(1.7)s

---> 3.42s = (250^2)/81

---> s = (250^2)/(81 * 3.42).

**Nima**)---> 0 = (250/9)^2 - 2(1.7)s

---> 3.42s = (250^2)/81

---> s = (250^2)/(81 * 3.42).

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#17

(Original post by

You're close!

That's the right formula as well.

v² = u² -2ds

v = ?

u = 100km/h = 27.78 m/s

d = 1.7 m/s²

s = 227 - 15 = 212 m

v² = (27.78)² - 2*1.7*212

v² = 771.73 - 720.8

v² = 50.93

v = 7.136

v = 7.14 m/s

=========

**Fermat**)You're close!

That's the right formula as well.

v² = u² -2ds

v = ?

u = 100km/h = 27.78 m/s

d = 1.7 m/s²

s = 227 - 15 = 212 m

v² = (27.78)² - 2*1.7*212

v² = 771.73 - 720.8

v² = 50.93

v = 7.136

v = 7.14 m/s

=========

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#18

hey dojo sorry i overslept this morning but i had a go. i can only get the right answer if i take 15m to mean 15 metres instead of 15 minutes as the total stopping time is about 16 seconds. but looking above i see the guys have already solved it. oh well

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(Original post by

hey dojo sorry i overslept this morning but i had a go. i can only get the right answer if i take 15m to mean 15 metres instead of 15 minutes as the total stopping time is about 16 seconds. but looking above i see the guys have already solved it. oh well

**magiccarpet**)hey dojo sorry i overslept this morning but i had a go. i can only get the right answer if i take 15m to mean 15 metres instead of 15 minutes as the total stopping time is about 16 seconds. but looking above i see the guys have already solved it. oh well

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