# I need help with this physics question

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#1
The speed of the train is v.During one period of its journey, the train accelerates from v = 30 m s–1 to v = 60 m s–1.The graph of F against v for this period is shown below.30 40 50 6050100150v / m s–1F / kN1. Use the graph to show that output power of the electric motor during this period isconstant at about 4 MW.
The speed of the train is v.

I've attached a photo of the graph. I also know that P=F*v
Last edited by IlikeCheese926jf; 1 month ago
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1 month ago
#2
Power = force x velocity, so you want to try at least 3 different points spread across the graph and see whether the constant (representing power) remains the same.
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1 month ago
#3
You can show the inconstant decrease of the power by calculating the slope of the curve. If it is inconstant, the slope is always different. And you have to show that this inconstance begins at 4MW.
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#4
(Original post by Kallisto)
You can show the inconstant decrease of the power by calculating the slope of the curve. If it is inconstant, the slope is always different. And you have to show that this inconstance begins at 4MW.
Power = force x velocity, so you want to try at least 3 different points spread across the graph and see whether the constant (representing power) remains the same.
Ahhhh thank you so much, it makes much more sense now
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1 month ago
#5
(Original post by IlikeCheese926jf)
Ahhhh thank you so much, it makes much more sense now
You are welcome! the constant of a graph can be proved so easily with the slope calculation, you need just to know how.
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