Physics P2 unofficial mark scheme.

was the rocket increasing or decreasing in velocity for the p2 paper ?

Reply 42

Decklan

OP

3

Original post by MrTechGamer

was the rocket increasing or decreasing in velocity for the p2 paper ?

Velocity would be increasing due to there being a resultant force.

Reply 43

Decklan

OP

3

Reps = motivation.

Once we hit 25 reps I'll post P3 :wink:

Reply 44

chemistryboi

1

Original post by Decklan

Reps = motivation.

Once we hit 25 reps I'll post P3 :wink:

pls upload now

Reply 45

[QUOTE="Decklan;56067645"]Velocity would be increasing due to there being a resultant force.[/QUOTEare you sure thats right , i mean if your right that would be great because thats what i put down , but someone on the forum suggested that the velocity is decreasing due to air resistance( which doesnt make sense to me)

Reply 46

Original post by Decklan

Velocity would be increasing due to there being a resultant force.

Nope, it would be decreasing... There was to upwards force, only that of air resistance, hence a downwards resultant force and an overall deceleration.

Reply 47

Decklan

OP

3

Original post by gecko242

Nope, it would be decreasing... There was to upwards force, only that of air resistance, hence a downwards resultant force and an overall deceleration.

Not quite sure which force was the overall resultant force, but if there was upward force then it would be increasing that would be if question didn't explicitly state air resistance would have an affect.

Reply 48

Original post by Decklan

Not quite sure which force was the overall resultant force, but if there was upward force then it would be increasing that would be if question didn't explicitly state air resistance would have an affect.

Problem here is that there was no upwards force. The rocket was launched with compressed air, and had no propulsion method of its own. The only forces acting upon it were air resistance and gravity, both downwards.

Reply 49

Original post by gecko242

Problem here is that there was no upwards force. The rocket was launched with compressed air, and had no propulsion method of its own. The only forces acting upon it were air resistance and gravity, both downwards.

I put down that velocity was increasing due to accelaration and increase in speed . I think that this would be correct as initially the rocket would accelarate , and it takes time for the resistive forces(air) to become equal to the weight of the rocket and it doesnt happen instantly .Think of a car.It would accelarate , till the resistive forces balance the driving force , then it would travel at constant velocity.

Reply 50

Original post by gecko242

Problem here is that there was no upwards force. The rocket was launched with compressed air, and had no propulsion method of its own. The only forces acting upon it were air resistance and gravity, both downwards.

p.s there must have been some force to allow the rocket to be launched upwards (resultant force) otherwise it wouldn't move and no air resistance would happen in the first place.

Reply 51

Original post by MrTechGamer

I put down that velocity was increasing due to accelaration and increase in speed . I think that this would be correct as initially the rocket would accelarate , and it takes time for the resistive forces(air) to become equal to the weight of the rocket and it doesnt happen instantly .Think of a car.It would accelarate , till the resistive forces balance the driving force , then it would travel at constant velocity.

The rocket is only accelerating off the launch tube, from there it slows down due to air resistance, its like a bullet from a gun. Since the rocket has no additional method of thrusting it cannot increase its own velocity.

Reply 52

For the majority of its flight (90%) it would be decreasing in velocity.

Reply 53

Original post by gecko242

The rocket is only accelerating off the launch tube, from there it slows down due to air resistance, its like a bullet from a gun. Since the rocket has no additional method of thrusting it cannot increase its own velocity.

Did you remember exactly what the question asked ?

Reply 54

rdj24

1

Original post by Ravioli99

Yepp

Posted from TSR Mobile

instead of putting Coulomb, could you put C? or did you have to put it in word form

Reply 55

When the rocket takes off, there is a large thrustfrom the engine but very little drag because the
rocket is moving slowly and air resistance is small.
The forces are unbalanced because there is a
large upward force but only a small downward force
and so the rocket has a large acceleration
in the direction of the larger force (upwards).As the rocket gets faster,
the drag increases and acceleration decreases
until the thrust and drag are equal in size.
Now the forces are balanced
and the rocket will continue with a constant velocity.The motion of the rocketis shown on the velocity - time graph below.

The red curve shows acceleration changing from large to small.
The blue line shows constant velocity.This is the same shape of velocity - time graph
as a falling object reaching its terminal velocity. P.s (In technical terms you could be right but for GCSE standard type questions they won't expect you to think to such a high degree of thinking , hence if your explanation is valid you should get the mark)

Reply 56

However the rocket was not launched by an engine but rather by compressed air i believe. This does not provide a constant thrust for a longer period of time but rather a short sharp burst, accelerating the rocket very quickly, but from there it starts to decelerate.

Reply 57

Conor1998

Original post by TaraMott

I also ticked graph B for the graphs on the last page but many are saying that its incorrect ?

I'm 99% sure it is right because that's the only graph that reached a terminal velocity

Reply 58

Original post by gecko242

However the rocket was not launched by an engine but rather by compressed air i believe. This does not provide a constant thrust for a longer period of time but rather a short sharp burst, accelerating the rocket very quickly, but from there it starts to decelerate.

If it said compressed air then you are probaly right , but in the spec it doesnt say that we should know how compressed air can change how the velocity of a rocket alters , so i think that they will accept increasing velocity and your explantion but reasoned.

Reply 59