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03 Nov 05
03 Nov 05
1 edit
okay, so one of my friends has asked me to help out with some physics questions. i've googled most of them, but can anyone help me with the following? it's been 18 years since i did physics at school and i'm afraid the only thing i can remember about the class was the foxy goth lass who sat in front of me. ANYWAY - can any of you bright sparks tell me the formulae for the following:
calculating accumulated heat energy
calculating speed as a body moves down a ramp
calculating work done against gravity and the normal force
any inspired answers, helpful comments or smart-arse wisecracks gratefully received
EDIT: i can provide context/relevant situations for the above calculations if anyone would like it...
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03 Nov 05
Originally posted by Edwardipov"calculating speed as a body moves down a ramp"
okay, so one of my friends has asked me to help out with some physics questions. i've googled most of them, but can anyone help me with the following? it's been 18 years since i did physics at school and i'm afraid the only thing i can remember about the class was the foxy goth lass who sat in front of me. ANYWAY - can any of you bright sparks tell me ...[text shortened]... i can provide context/relevant situations for the above calculations if anyone would like it...
Distance = speed x time
I'm not sure about the others, I could check but it would take a while and I really don't have the time.
03 Nov 05
Originally posted by Bad wolfIf the ramp is frictionless and makes an angle a with the horizontal, then the body will accelerate in proportion to the sine of a.
"calculating speed as a body moves down a ramp"
Distance = speed x time
I'm not sure about the others, I could check but it would take a while and I really don't have the time.
03 Nov 05
Originally posted by royalchickennice one, cheers for the post. i understand what you're saying, but is there a formula for calculating the actual acceleration/speed?
If the ramp is frictionless and makes an angle a with the horizontal, then the body will accelerate in proportion to the sine of a.
03 Nov 05
2 edits
Originally posted by sasquatch672cheers sasquatch, thanks for taking the time. for the benefit of yrself and anyone else who might be interested, the specific problem is as follows:
Your heat question:
Q = A*Cp dT
Where Q = units of energy, A = area of heat transfer, Cp = coefficient of heat transfer, and dT = Temperature difference.
Send me the problem.
A lady in a wheelchair, with combined mass of 90 kg, is about to embark down a hill with a 14% decline. The vertical distance from the top of the hill to the bottom is 2 metres. There will be an energy transfer from the potential energy she contains at the top of the hill, to kinetic energy and heat as she moves down the hill.
If the lady in the wheelchair starts down the hill and doesn’t apply her brakes, what will her speed be at the bottom of the hill?
Calculate the accumulated heat energy produced by the application of the brakes when the lady is positioned:
at the top of the hill,
at a vertical distance of 1 metre down the hill,
at the bottom of the hill.
And finally, At the bottom of the hill the lady decides to turn around and ascend the hill. when she has travelled distance m, 6 metres up the hill as shown in the diagram, what is the work done against gravity, and the normal force, N, with respect to the hill?
there is a diagram which shows the relationship between all the parties involved, which i have parked at http://www.twenty3.demon.co.uk/diagram.gif
does this make sense?
03 Nov 05
Originally posted by sasquatch672yes, i've probably used all sorts of incorrect terminology i'm afraid - i stopped doing physics in 1989 and have since forgotten pretty much everything i ever learned. thanks again for taking the time to help though, it's much appreciated. any more questions, just let me know - or PM if you'd prefer to take it off-forum.
Draw your free-body diagram for work done "opposing gravity and the normal force".
For a body on a surface and not fallng, the normal force balances gravity - the surface pushes up on the body with the same force that gravity is pulling down on the body. Also, you referred to "work done" incorrectly. The units of work are force*distance, in S ...[text shortened]... red. So I'm not sure what you're looking for. Perhaps if you sent this problem over as well.