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Mechanics question

How do you do part ii)? i)Yes, the range is 70.4m ii)32.7ms^-1
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Original post by Kalabamboo
How do you do part ii)? i)Yes, the range is 70.4m ii)32.7ms^-1


He says that under air resistance, any jump’s normal range will be reduced by 40%.

Lets look at the scenario where without air resistance then range is R for some speed. Then he will make the jump if 0.6R > 50. Hence, look at the very minimum case where 0.6R = 50 hence R = 50/0.6. What is the speed needed such that this is the range?
the range must be reduced by 40% to make 50m... so the range is 83 and 1/3 m.

Vcos25°*T = 83⅓

where T is the total time for the flight.

you can find the time it takes to reach the top by finding when the vertical velocity is zero. then double this time to get T.
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Kalabamboo
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Original post by RDKGames
He says that under air resistance, any jump’s normal range will be reduced by 40%.

Lets look at the scenario where without air resistance then range is R for some speed. Then he will make the jump if 0.6R > 50. Hence, look at the very minimum case where 0.6R = 50 hence R = 50/0.6. What is the speed needed such that this is the range?


Thank you! What about this question - could you help with this as well please?
Stuck on iii) and iv). The lowest speed and greatest speed bit is confusing me. i)0.47s ii)0.64s iii)25.5ms^-1 iv) 28.8ms^-1
Reply 4
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Kalabamboo
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Original post by the bear
the range must be reduced by 40% to make 50m... so the range is 83 and 1/3 m.

Vcos25°*T = 83⅓

where T is the total time for the flight.

you can find the time it takes to reach the top by finding when the vertical velocity is zero. then double this time to get T.


Thank you! What about this question - could you help with this as well please?
Stuck on iii) and iv). The lowest speed and greatest speed bit is confusing me. i)0.47s ii)0.64s iii)25.5ms^-1 iv) 28.8ms^-1
iii) you must place the ball at the point ( 12, 0.91 )

use this formula with angle = 0 degrees to find vo :

iv) as above but work with the point ( 18.4, 0 )
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Kalabamboo
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Original post by the bear
iii) you must place the ball at the point ( 12, 0.91 )

use this formula with angle = 0 degrees to find vo :



Thanks but is this A level?
Original post by Kalabamboo
Thanks but is this A level?


yes
Reply 9
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Kalabamboo
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Original post by the bear
yes


I have never seen that formula before - I do mei maths.:tongue:

Out of interest, for the question before(part ii) below:The horizontal acceleration is zero, right? So what about the air resistance? Doesn't that result in horizontal acceleration? Thanks
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Original post by Kalabamboo
...


you are right... air resistance would affect both the horizontal and vertical velocities...

however to do the question you need to use the original suvat model but with the increased range.
Original post by the bear
you are right... air resistance would affect both the horizontal and vertical velocities...

however to do the question you need to use the original suvat model but with the increased range.


Thanks!:smile:

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