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# Physics AS projectiles questions no calculation

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the questions are b I) from the plane question and question e) they are not from the same paper. I did the plane question first and followed it MS to do the second question but thyre different. can someone explain the ans to me pls
thank you

(the graph question is just incase it needs to be referred to)
Attached Images

2. (Original post by Exotic-L)
the questions are b I) from the plane question and question e) they are not from the same paper. I did the plane question first and followed it MS to do the second question but thyre different. can someone explain the ans to me pls
thank you

(the graph question is just incase it needs to be referred to)
The answers are saying the same thing in both cases.

Please realise that mark schemes are an aid for people marking and not meant for students as model answers. The objective is to obtain consistency between markers and as an aid to avoid ambiguity.

1) Taking the first question:

The question tells us to ignore air resistance. That immediately tells us that no forces other than gravity will act on the sack.

No air resistance means no change in the horizontal velocity of the sack as it leaves the aircraft. From Newton, the sack will continue in a horizontal straight line because there is no force in the horizontal direction acting to change it's motion in the horizontal direction.

However, there is still the force of gravity acting to accelerate the sack towards the earth. And again from Newton, the sack velocity in the vertical direction will increase because there is the force of gravity acting on it in the vertical direction. i.e. the force of gravity causes the sack to accelerate vertically.

But since both the aircraft and the sack are travelling at the same velocity in the horizontal direction (with no horizontal force acting in the horizontal direction), the sack will hit the ground whilst still directly underneath the aircraft, even though both have travelled a considerable distance horizontally.

2) The answer to the second question should now be apparent.
3. (Original post by uberteknik)
The answers are saying the same thing in both cases.

Please realise that mark schemes are an aid for people marking and not meant for students as model answers. The objective is to obtain consistency between markers and as an aid to avoid ambiguity.

1) Taking the first question:

The question tells us to ignore air resistance. That immediately tells us that no forces other than gravity will act on the sack.

No air resistance means no change in the horizontal velocity of the sack as it leaves the aircraft. From Newton, the sack will continue in a horizontal straight line because there is no force in the horizontal direction acting to change it's motion in the horizontal direction.

However, there is still the force of gravity acting to accelerate the sack towards the earth. And again from Newton, the sack velocity in the vertical direction will increase because there is the force of gravity acting on it in the vertical direction. i.e. the force of gravity causes the sack to accelerate vertically.

But since both the aircraft and the sack are travelling at the same velocity in the horizontal direction (with no horizontal force acting in the horizontal direction), the sack will hit the ground whilst still directly underneath the aircraft, even though both have travelled a considerable distance horizontally.

2) The answer to the second question should now be apparent.
thank you soo much for the reply. I sort of get it now. but in the second question would it be possible for the stone to land in-front of the air balloon since they are both moving in the same horizontal velocity? like the ans for question b, sould it not follow path A?
4. (Original post by Exotic-L)
thank you soo much for the reply. I sort of get it now. but in the second question would it be possible for the stone to land in-front of the air balloon since they are both moving in the same horizontal velocity? like the ans for question b, sould it not follow path A?
I think you are misinterpreting the diagram for the aircraft. The sack cannot land in front of the aircraft. The stone cannot land in front of the balloon. The diagram has omitted to show that the aircraft has also moved horizontally in the same time as the sack.

The diagram shows the path the sack travels as if observed by a person on the ground watching it fall.

The diagram does not show the path the aircraft travels in that same time.

The attached diagram of a similar situation will make it clearer. Note the aircraft has also travelled some distance and that the correct answer is b). i.e. the sack lands directly beneath the aircraft.

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