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It's wrong. C shows that there is constant acceleration then when the chute is pulled there is a large drop in acceleration but then rapidly rises.
Reply 2
Original post by Vikingninja
It's wrong. C shows that there is constant acceleration then when the chute is pulled there is a large drop in acceleration but then rapidly rises.


So the answer should be D, since the acceleration increases then becomes constant ?
Original post by ksrw395
So the answer should be D, since the acceleration increases then becomes constant ?


Actually no sorry I'm an idiot it is C sorry. Thought that on C it went back up to its original but looked second time and it rose up and stopped at 0. Others are incorrect since they show an increase in acceleration when its in the positive.
Reply 4
Original post by Vikingninja
Actually no sorry I'm an idiot it is C sorry. Thought that on C it went back up to its original but looked second time and it rose up and stopped at 0. Others are incorrect since they show an increase in acceleration when its in the positive.


Haha no problem
Thanks! :smile:
C is correct.

The jumper accelerates under constant gravitational acceleration (velocity increases) until his chute opens.

As the chute opens, he decelerates (curve goes negative) rapidly and attains a constant velocity at which time the acceleration is zero.
Original post by uberteknik
C is correct.

The jumper accelerates under constant gravitational acceleration (velocity increases) until his chute opens.

As the chute opens, he decelerates (curve goes negative) rapidly and attains a constant velocity at which time the acceleration is zero.



Sorry this is an old post, but what about if air resistance is taken into account?
Original post by marinacalder
Sorry this is an old post, but what about if air resistance is taken into account?


That of the parachute is
Original post by marinacalder
Sorry this is an old post, but what about if air resistance is taken into account?


The deceleration/negative acceleration is caused by increased air resistance.
Original post by marinacalder
Sorry this is an old post, but what about if air resistance is taken into account?


air resistance before the diver opened his chute would round off the start of the 'knee' a bit - terminal velocity of a skydiver is ~50 m/s so after 2.5 seconds the diver would be going maybe half that, so getting about 1/4 of the resistance at terminal velocity... air resistance would be starting to be get quite significant.
i have a problem with this exact question because i thought the acceleration would decrease to zero, then stop and be constant. i dont fully understand why it continues further down? is it because of air resistance? If so please expound? but if the acceleration is negative, doesnt that mean its moving in the opposite direction, and does that even make sense then?
Original post by Mikaela Mitchell
i have a problem with this exact question because i thought the acceleration would decrease to zero, then stop and be constant. i dont fully understand why it continues further down? is it because of air resistance? If so please expound? but if the acceleration is negative, doesnt that mean its moving in the opposite direction, and does that even make sense then?

Because the air resistance will cause a deceleration
A negative acceleration means a deceleration, the velocity decreases
Original post by Mikaela Mitchell
i have a problem with this exact question because i thought the acceleration would decrease to zero, then stop and be constant. i dont fully understand why it continues further down? is it because of air resistance? If so please expound? but if the acceleration is negative, doesnt that mean its moving in the opposite direction, and does that even make sense then?



Initially, the acceleration and velocity are in the same direction i.e. pointing down toward the Earth. When the parachute is opened at t = 2.5s, air resistance increases rapidly. The air resistance is much greater than the weight of the parachutist, so the direction of acceleration changes rapidly from downwards to upward (i.e. against the motion of the parachutist). As a result, the motion of the parachutist slows down. When the speed of the parachutist slows down, air resistance decreases. The magnitude of the acceleration will also decrease and reach zero eventually when the terminal velocity is reached.

Note that a number of the helpers mention that negative acceleration means deceleration. This is NOT always the case. The interpretation of negative acceleration should take into account the direction of the velocity.
Original post by Eimmanuel
Initially, the acceleration and velocity are in the same direction i.e. pointing down toward the Earth. When the parachute is opened at t = 2.5s, air resistance increases rapidly. The air resistance is much greater than the weight of the parachutist, so the direction of acceleration changes rapidly from downwards to upward (i.e. against the motion of the parachutist). As a result, the motion of the parachutist slows down. When the speed of the parachutist slows down, air resistance decreases. The magnitude of the acceleration will also decrease and reach zero eventually when the terminal velocity is reached.

Note that a number of the helpers mention that negative acceleration means deceleration. This is NOT always the case. The interpretation of negative acceleration should take into account the direction of the velocity.

Wow, This helped loads. Thank you
Reply 14
This is clearly if there is no air resistance. If there was to be air resistance, wouldnt the resultant force begin to decrease, causing a decreasing value of acceleration until it becomes zero at terminal velocity. Then the graph will continue after 2.5 like at C?
Please correct me if i am wrong
Original post by %20%20
This is clearly if there is no air resistance. If there was to be air resistance, wouldnt the resultant force begin to decrease, causing a decreasing value of acceleration until it becomes zero at terminal velocity. Then the graph will continue after 2.5 like at C?
Please correct me if i am wrong


Hi, this thread has existed for over 5 years, so it would be great if you start a new thread and link to it.
I understand you are new to TSR and may not understand this "rule".

I will try to explain your thinking.
First of all, I don't understand what you mean by there is no air resistance.
If there is no air resistance, how can your reasoning lead to option C?

Original post by %20%20
... If there was to be air resistance, wouldnt the resultant force begin to decrease, causing a decreasing value of acceleration until it becomes zero at terminal velocity. Then the graph will continue after 2.5 like at C? ...


Seems to be good. :smile:

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