# A Level Maths Mechanics Help pls

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Last Question of my HW and im stuck pls help asap its due tomorrow

In an orienteering competition, a competitor moves in a straight line past three checkpoints, P, Q and R, where PQ = 2.4 KM and QR = 11.5 KM. The competitor is modelled as a particle moving with constant acceleration. She takes 1 hour to travel from P to Q and 1.5 hours to travel from Q to R. Find:

a) the acceleration of the competitor

b) her speed at the instant she passes P

In an orienteering competition, a competitor moves in a straight line past three checkpoints, P, Q and R, where PQ = 2.4 KM and QR = 11.5 KM. The competitor is modelled as a particle moving with constant acceleration. She takes 1 hour to travel from P to Q and 1.5 hours to travel from Q to R. Find:

a) the acceleration of the competitor

b) her speed at the instant she passes P

Last edited by prajeetboi; 3 weeks ago

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#2

(Original post by

Last Question of my HW and im stuck pls help asap its due tomorrow

In an orienteering competition, a competitor moves in a straight line past three checkpoints, P, Q and R, where PQ = 2.4 KM and QR = 11.5 KM. The competitor is modelled as a particle moving with constant acceleration. She takes 1 hour to travel from P to Q and 1.5 hours to travel from Q to R. Find:

a) the acceleration of the competitor

b) her speed at the instant she passes

**MikeOxlong69**)Last Question of my HW and im stuck pls help asap its due tomorrow

In an orienteering competition, a competitor moves in a straight line past three checkpoints, P, Q and R, where PQ = 2.4 KM and QR = 11.5 KM. The competitor is modelled as a particle moving with constant acceleration. She takes 1 hour to travel from P to Q and 1.5 hours to travel from Q to R. Find:

a) the acceleration of the competitor

b) her speed at the instant she passes

Last edited by mqb2766; 3 weeks ago

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i know 5 suvat equation which are as follows:

u = v - at

2s/(u+v) = t

v^2 = U^2 + 2as

s = Vt - (1/2)at^2

S = ut + (1/2)at^2

i cant figure out which one to use. i can only derive 2 pieces of information, and i can't figure out the third to solve for acceleration.

u = v - at

2s/(u+v) = t

v^2 = U^2 + 2as

s = Vt - (1/2)at^2

S = ut + (1/2)at^2

i cant figure out which one to use. i can only derive 2 pieces of information, and i can't figure out the third to solve for acceleration.

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#4

(Original post by

i know 5 suvat equation which are as follows:

u = v - at

2s/(u+v) = t

v^2 = U^2 + 2as

s = Vt - (1/2)at^2

S = ut + (1/2)at^2

i cant figure out which one to use. i can only derive 2 pieces of information, and i can't figure out the third to solve for acceleration.

**MikeOxlong69**)i know 5 suvat equation which are as follows:

u = v - at

2s/(u+v) = t

v^2 = U^2 + 2as

s = Vt - (1/2)at^2

S = ut + (1/2)at^2

i cant figure out which one to use. i can only derive 2 pieces of information, and i can't figure out the third to solve for acceleration.

However, you have two sets of such information. Can you think how you can use two (possible the same equation with different s and t) to eliminate the need for the third bit of information.

Id concentrate on the last equation and think about P->Q and P->R.

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#5

(Original post by

Last Question of my HW and im stuck pls help asap its due tomorrow

In an orienteering competition, a competitor moves in a straight line past three checkpoints, P, Q and R, where PQ = 2.4 KM and QR = 11.5 KM. The competitor is modelled as a particle moving with constant acceleration. She takes 1 hour to travel from P to Q and 1.5 hours to travel from Q to R. Find:

a) the acceleration of the competitor

b) her speed at the instant she passes B

**MikeOxlong69**)Last Question of my HW and im stuck pls help asap its due tomorrow

In an orienteering competition, a competitor moves in a straight line past three checkpoints, P, Q and R, where PQ = 2.4 KM and QR = 11.5 KM. The competitor is modelled as a particle moving with constant acceleration. She takes 1 hour to travel from P to Q and 1.5 hours to travel from Q to R. Find:

a) the acceleration of the competitor

b) her speed at the instant she passes B

S = 2.4+11.5

T=2.5hrs

A=?

U=0

What eqtn can you use?

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#6

(Original post by

Looks pretty simple.

S = 2.4+11.5

T=2.5hrs

A=?

U=0

What eqtn can you use?

**boulderingislife**)Looks pretty simple.

S = 2.4+11.5

T=2.5hrs

A=?

U=0

What eqtn can you use?

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#7

(Original post by

It doesn't say u=0 anywhere?

**mqb2766**)It doesn't say u=0 anywhere?

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oh i see now - its simultaneous equations

i got these equations:

2.4 = u+ (1/2)a

13.9 = 2.5u + 3.125a

solved this for:

u = 0.293 ms^-1

a = 4.2 ms^-2

and then for b:

isnt it just 0.293 ms^-1??

because we worked that out in part a no??

let me know if this is right

i got these equations:

2.4 = u+ (1/2)a

13.9 = 2.5u + 3.125a

solved this for:

u = 0.293 ms^-1

a = 4.2 ms^-2

and then for b:

isnt it just 0.293 ms^-1??

because we worked that out in part a no??

let me know if this is right

Last edited by prajeetboi; 3 weeks ago

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#9

(Original post by

and then for b:

isnt it just 0.293 ms^-1??

because we worked that out in part a no??

let me know if this is right

**MikeOxlong69**)and then for b:

isnt it just 0.293 ms^-1??

because we worked that out in part a no??

let me know if this is right

**B**but that point is never mentioned or defined in the rest of the question.

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#10

(Original post by

oh i see now - its simultaneous equations

i got these equations:

2.4 = u+ (1/2)a

13.9 = 2.5u + 3.125a

solved this for:

u = 0.293 ms^-1

a = 4.2 ms^-2

and then for b:

isnt it just 0.293 ms^-1??

because we worked that out in part a no??

let me know if this is right

**MikeOxlong69**)oh i see now - its simultaneous equations

i got these equations:

2.4 = u+ (1/2)a

13.9 = 2.5u + 3.125a

solved this for:

u = 0.293 ms^-1

a = 4.2 ms^-2

and then for b:

isnt it just 0.293 ms^-1??

because we worked that out in part a no??

let me know if this is right

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(Original post by

We don't know what point is actually meant fthor (b): you wrote

**DFranklin**)We don't know what point is actually meant fthor (b): you wrote

**B**but that point is never mentioned or defined in the rest of the question.its meant to say P

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#12

**MikeOxlong69**)

oh i see now - its simultaneous equations

i got these equations:

2.4 = u+ (1/2)a

13.9 = 2.5u + 3.125a

solved this for:

u = 0.293 ms^-1

a = 4.2 ms^-2

and then for b:

isnt it just 0.293 ms^-1??

because we worked that out in part a no??

let me know if this is right

In a) you could just eliminate u and solve for a.

Then in b), you could find u, assuming that's the question asked - passing through P?

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#13

(Original post by

thanks for spotting that, i'll change the original post now

its meant to say P

**MikeOxlong69**)thanks for spotting that, i'll change the original post now

its meant to say P

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(Original post by

Units need converting.

**boulderingislife**)Units need converting.

when u solve the equations u get the following:

u = 0.293 kmh^-1

a = 4.2 kmh^-2

which when converted to SI units gives:

u = 0.293*1000*(3600)^-1 = 0.0814 ms^-1

a = 4.2*1000*(3600)^-2 = 3.24*10^-4 ms^-2

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(Original post by

omg im so dumb lol

when u solve the equations u get the following:

u = 0.293 kmh^-1

a = 4.2 kmh^-2

which when converted to SI units gives:

u = 0.293*1000*(3600)^-1 = 0.0814 ms^-1

a = 4.2*1000*(3600)^-2 = 3.24*10^-4 ms^-2

**MikeOxlong69**)omg im so dumb lol

when u solve the equations u get the following:

u = 0.293 kmh^-1

a = 4.2 kmh^-2

which when converted to SI units gives:

u = 0.293*1000*(3600)^-1 = 0.0814 ms^-1

a = 4.2*1000*(3600)^-2 = 3.24*10^-4 ms^-2

right????

boulderingislife

mqb2766

Last edited by prajeetboi; 3 weeks ago

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#16

**MikeOxlong69**)

oh i see now - its simultaneous equations

i got these equations:

2.4 = u+ (1/2)a

13.9 = 2.5u + 3.125a

solved this for:

u = 0.293 ms^-1

a = 4.2 ms^-2

and then for b:

isnt it just 0.293 ms^-1??

because we worked that out in part a no??

let me know if this is right

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reply

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