A level physics questions that I need help with

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Fadhi
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#1
Report Thread starter 1 year ago
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I don’t understand these questions
a person cycles to a destination with the wind at 8m/s and returns home without stopping, against the wind, at 4m/s
What is the average speed
What is the velocity
And
A ball is thrown vertically at 20.0m/s from the surface of the earth. With what speed would it have to be thrown at Jupiter, where g=22.5m/s2, in order to reach the same height

For the first question I got
Average speed = (-4+8)/2=2
Velocity= 0
I think this is wrong but i’m Not sure how i’m supposed to do it
For the second question I keep getting weird answers. So can you plz help me
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teilchen
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#2
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(Original post by Fadhi)
I don’t understand these questions
a person cycles to a destination with the wind at 8m/s and returns home without stopping, against the wind, at 4m/s
What is the average speed
What is the velocity
And
A ball is thrown vertically at 20.0m/s from the surface of the earth. With what speed would it have to be thrown at Jupiter, where g=22.5m/s2, in order to reach the same height

For the first question I got
Average speed = (-4 8)/2=2
Velocity= 0
I think this is wrong but i’m Not sure how i’m supposed to do it
For the second question I keep getting weird answers. So can you plz help me
I’m pretty sure your answer for the speed of the first one is the answer for velocity (only velocity has direction speed doesn’t have direction) so the speed is just 8 4/2 which is 6

And for the second one is it just 20/9.81 (g on earth) then times that by g on the other planet (not so sure about this one tho pretty sure my answer to the first one is right tho)
Last edited by teilchen; 1 year ago
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Fadhi
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#3
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it’s says on the paper that neither answer is 6 and that I need to think of the time for each journey
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Physics Enemy
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#4
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(Original post by Fadhi)
1) A person cycles to a destination with the wind at 8 m/s, returns home without stopping against the wind, at 4 m/s. Find the average: speed, velocity

2) A ball is thrown vertically at 20 m/s from the surface of the earth. With what speed must it be thrown at from Jupiter, where g = 22.5 m/s^2, to reach the same height.
1) average speed = total distance/total time
= 2x/(x/8 + x/4) = 2/(3/8) = 16/3 m/s
average velocity = total displacement/total time = 0

2) Earth: u = 20, a = -g, v = 0: 0 = 400 - 2gs => s = 200/g
Jupiter: a = -22.5, s = 200/g, v = 0: 0 = u^2 - 45*200/g
=> u = sqrt(9*5*100*2/g) = 30sqrt(10/g) m/s
Last edited by Physics Enemy; 1 year ago
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Fadhi
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#5
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Thank you so much
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