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Please can someone show me how to answer this physics question

A car starts from rest and travels upwards along a straight road inclined at an angle of 5.0o
to the
horizontal,
The speed of the car increases at a constant rate and is 28 m s-1 at the top of the slope.
Determine, for the car travelling up the slope,
i) its acceleration;
ii) the time taken to travel the length of the slope;
iii) the gain in kinetic energy for the car;
iv) the gain in gravitational potential energy for the car;
v) the useful power output of the car's engine.

I'm completely lost and have no idea can someone please shoe me how to answer it

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Is this all of the info? Do you have a picture or stuff like distance or height?
Reply 2
Avatar for Amberinho
Amberinho
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Original post by Vikingninja
Is this all of the info? Do you have a picture or stuff like distance or height?


Yeah sorry here it is
Screenshot_20180204-205300.png194.0KB
Original post by Amberinho
Yeah sorry here it is


the 450 m was the missing piece of the jigsaw.
Reply 4
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Amberinho
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Original post by the bear
the 450 m was the missing piece of the jigsaw.


Ahaha sorry I didn't realise
so now you can use a suvat equation...

u = 0

v = 28

s = 450

a = ???
i V^2 = u^2 +2as
ii s = ut + 0.5at^2, rearrange as u = 0.
iii Kinetic energy equation
iv Potential energy equation, work out h using trigonometry
v Believe you only need kinetic energy for this, power is work/time and you got time from ii. Only thing that I am unsure of is energy applied though I'm guessing just kinetic because I wouldn't say the potential is useful.
(edited 6 years ago)
Reply 7
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phys981
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Original post by Vikingninja

v Believe you only need kinetic energy for this, power is work/time and you got time from ii. Only thing that I am unsure of is energy applied though I'm guessing just kinetic because I wouldn't say the potential is useful.

I'd say you need both - the car has to get up the slope therefore the GPE is important as well.
How did y'all get to this thread so quickly :frown: Physics is my strongish area.

What everyone above said is correct, I'll rep em for you.


----------------------------------------
The bear: PRSOM
Original post by rsk
I'd say you need both - the car has to get up the slope therefore the GPE is important as well.


I thought that the GPE is stored energy from the height gained and so doesn't help with moving up the slope.
It doesn't help moving up the slope, no. But that GPE has to come from somewhere. The car increases BOTH its KE and its GPE and both of those come from the engine.
Original post by rsk
It doesn't help moving up the slope, no. But that GPE has to come from somewhere. The car increases BOTH its KE and its GPE and both of those come from the engine.


That's the thing that gets me with this question. It specifies useful energy output but the GPE I would've thought wouldn't be useful unless it moves down the slope though I haven't done these questions in a while so I'm not sure if stored energy is considered useful when it isn't being used.
If you didn't give the car the GPE, it couldn't get up the slope. The 'useful' you can think of as applying to the output of the engine and not the GPE store at the top of the slope.
Reply 13
Avatar for Amberinho
Amberinho
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Original post by Vikingninja
i Change in velocity over distance
ii s = ut + 0.5at^2, rearrange as u = 0.
iii Kinetic energy equation
iv Potential energy equation, work out h using trigonometry
v Believe you only need kinetic energy for this, power is work/time and you got time from ii. Only thing that I am unsure of is energy applied though I'm guessing just kinetic because I wouldn't say the potential is useful.


So other kinetic energy question would I use trigonometry to find a component of the velocity which I would then square or use 28?
Energy is a scalar, direction and components don't matter, use the 28.
Original post by rsk
If you didn't give the car the GPE, it couldn't get up the slope. The 'useful' you can think of as applying to the output of the engine and not the GPE store at the top of the slope.


So GPE serves to get it up the hill whilst more available work from the engine allows it to accelerate?
Original post by Amberinho
So other kinetic energy question would I use trigonometry to find a component of the velocity which I would then square or use 28?


You just use velocity at the top of slope and the kinetic energy is gained from the increase.
Reply 17
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Amberinho
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Original post by Bulletzone
How did y'all get to this thread so quickly :frown: Physics is my strongish area.

What everyone above said is correct, I'll rep em for you.


----------------------------------------
The bear: PRSOM


Thank you😀
Original post by Vikingninja
So GPE serves to get it up the hill whilst more available work from the engine allows it to accelerate?


Yes

Original post by Vikingninja
i Change in velocity over distancel.


Ouch! Be careful here, check your equations of motion.
Then once you have the acceleration it makes part ii simpler as well.
(edited 6 years ago)
Reply 19
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Amberinho
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Original post by rsk
Energy is a scalar, direction and components don't matter, use the 28.


Thanks😀

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