# Energy concepts

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#1
How do you find the component of a cyclist's (of mass 100kg) weight acting down a hill inclined at 10 degrees to the horizontal? Where she keeps her brakes on so that she travels at a steady speed of 6m/s and the brakes are the only force opposing the motion
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6 years ago
#2
(Original post by bubblegum21)
How do you find the component of a cyclist's (of mass 100kg) weight acting down a hill inclined at 10 degrees to the horizontal? Where she keeps her brakes on so that she travels at a steady speed of 6m/s and the brakes are the only force opposing the motion

Could you post the complete question please.
The component of the weight down the incline (parallel to it) does not depend on whether or not the brakes are on.
There is clearly more to the question.
Tell us what you've done on it so far.
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#3
(Original post by Stonebridge)
Could you post the complete question please.
The component of the weight down the incline (parallel to it) does not depend on whether or not the brakes are on.
There is clearly more to the question.
Tell us what you've done on it so far.
A cyclist of mass 100kg is freewheeling down a hill at 10 degrees to the horizontal. She keeps the brakes on so that she travels at a steady speed of 6m/s.
The brakes provide the only force opposing the motion.
Calculate (a) the weight of the cyclist and (b) the component of her weight acting down the hill. have calculated her weight to be 980N but I am unsure how to answer part (b). Any suggestions?
0
6 years ago
#4
(Original post by bubblegum21)
A cyclist of mass 100kg is freewheeling down a hill at 10 degrees to the horizontal. She keeps the brakes on so that she travels at a steady speed of 6m/s.
The brakes provide the only force opposing the motion.
Calculate (a) the weight of the cyclist and (b) the component of her weight acting down the hill. have calculated her weight to be 980N but I am unsure how to answer part (b). Any suggestions?
Do you know how to find the component of a force?
The weight acts vertically downwards (you have the value of this now) and you need to find the component of that force acting at 10 degs to the horizontal, which is 80 degs to the vertical.
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#5
(Original post by Stonebridge)
Do you know how to find the component of a force?
The weight acts vertically downwards (you have the value of this now) and you need to find the component of that force acting at 10 degs to the horizontal, which is 80 degs to the vertical.
I know how to find vertical and horizontal components but I'm confused as to how to apply this knowledge to the question.
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6 years ago
#6
Draw a diagram.
What angle does the vertical weight make to a line parallel to and down the slope. (answer given in my last post)?
What is the component of that vertical weight in that direction?
You can find components of a force in any two mutually perpendicular directions. They don't have to be vertical and horizontal. Here the two directions are parallel to and perpendicular to the incline.
You calculate the components in exactly the same way. One is cos and the other is sin.
You are calculating the component of the weight (which is vertical) in a direction down the slope, which is at 80 degs to that vertical.
1
3 weeks ago
#7
do you know to find the braking force from the bike
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