HSC Physics Question Thread

[justwannawish]

Here are a couple general tips:

- Max horizontal range occurs when the angle is 45 degrees
- Vy = 0 at max height
- Ux = Vx -> Horizontal motion has no acceleration
- When calculating 't' using the equations from the 'y' axis of motion, it is only the time to reach half the total trajectory time (i.e. when Vy = 0), but the equation Δx = Uxt considers the value of t for the entire trajectory.
- If a projectile is launched horizontally (from the max height):
    -> Uy = 0
    -> U = Ux
    -> Δy should be taken as a negative value generally in these cases

thank you so much!

Could someone please advise me what to cut down for the following exam question? I feel like I talked for too long 

Discuss the contribution of von Braun to the development of space exploration (4 marks) .

Spoiler

Wernher von Braun, a German aerospace engineer, has made many significant contributions to space exploration, regarding liquid-fuelled propelled rockets, the Jupiter C, Saturn 5 and V2 rocket.

Working with Hermann Oberth, von Braun designed liquid-fuel propelled rockets, which can be combined with greater efficiency and, thus, greater power than the solid-fuel engines. His work controlled the g-forces experienced by astronauts and varied the thrust produced by the rocket, with these liquid fuels now used in modern satellites and in his own Saturn V thrust rocket that powered the Apollo missions.

After defecting, he developed advanced rockets for space exploration, including the Jupiter-C, a modified Redstone ballistic missile that launched the US’s first satellite, Explorer 1, into orbit. Shaping new research and developing space travel, his contributions have enhanced existing knowledge of space exploration. As NASA’s Marshall space flight centre’s director, he later led and constructed the Saturn 5 Rocket, the only space launch vehicle to launch missions that carried humans beyond low Earth orbit. His project also was the booster that launched Apollo 11 into outer space, sending man to the moon and ultimately developing rocket design, fabrication and space travel operation.

However, his role as the director and designer of the V2 rocket, the first intercontinental ballistic missile, had a controversial effect on space exploration. Demonstrating the use of gyroscopes to stabilise large rockets, the V2 was launched 80km above Earth in a 190km trajectory. Its liquid ethanol-oxygen propellent and bullet structure was structured to attack London during World War II, a detriment to rocketry, but was later mimicked in the rockets of the US and Soviet space exploration to launch their space programs .

[CyberScopes]

thank you so much!

Could someone please advise me what to cut down for the following exam question? I feel like I talked for too long 

Discuss the contribution of von Braun to the development of space exploration (4 marks) .

Spoiler

Wernher von Braun, a German aerospace engineer, has made many significant contributions to space exploration, regarding liquid-fuelled propelled rockets, the Jupiter C, Saturn 5 and V2 rocket.

Working with Hermann Oberth, von Braun designed liquid-fuel propelled rockets, which can be combined with greater efficiency and, thus, greater power than the solid-fuel engines. His work controlled the g-forces experienced by astronauts and varied the thrust produced by the rocket, with these liquid fuels now used in modern satellites and in his own Saturn V thrust rocket that powered the Apollo missions.

After defecting, he developed advanced rockets for space exploration, including the Jupiter-C, a modified Redstone ballistic missile that launched the US’s first satellite, Explorer 1, into orbit. Shaping new research and developing space travel, his contributions have enhanced existing knowledge of space exploration. As NASA’s Marshall space flight centre’s director, he later led and constructed the Saturn 5 Rocket, the only space launch vehicle to launch missions that carried humans beyond low Earth orbit. His project also was the booster that launched Apollo 11 into outer space, sending man to the moon and ultimately developing rocket design, fabrication and space travel operation.

However, his role as the director and designer of the V2 rocket, the first intercontinental ballistic missile, had a controversial effect on space exploration. Demonstrating the use of gyroscopes to stabilise large rockets, the V2 was launched 80km above Earth in a 190km trajectory. Its liquid ethanol-oxygen propellent and bullet structure was structured to attack London during World War II, a detriment to rocketry, but was later mimicked in the rockets of the US and Soviet space exploration to launch their space programs .

Its a very well put answer. Personally, I would remove some of the specific details that doesnt exactly add much value to the question, especially since u have a lot of examples in the answers and history (such as in the last paragraph)

[justwannawish]

Its a very well put answer. Personally, I would remove some of the specific details that doesnt exactly add much value to the question, especially since u have a lot of examples in the answers and history (such as in the last paragraph)

Thank you! I'll try to reduce it, but wanted to discuss both sides of the issue so that's why I included the history
Could you also help me with finding details of projectile motion with air resistance taken into factor? Why do angles larger than 45 produce longer ranges?

Sorry for asking so many questions!

[blasonduo]

Thank you! I'll try to reduce it, but wanted to discuss both sides of the issue so that's why I included the history
Could you also help me with finding details of projectile motion with air resistance taken into factor? Why do angles larger than 45 produce longer ranges?

Sorry for asking so many questions!

In the HSC physics course, we do not need to factor in air resistance into the equations, so don't worry about that.

Also, 45 degrees will always give the furthest range, unless given more velocity. There is no way a projectile angles at 89 degrees to the horizontal will travel further than one 45 degrees to the horizontal

[justwannawish]

In the HSC physics course, we do not need to factor in air resistance into the equations, so don't worry about that.

Also, 45 degrees will always give the furthest range, unless given more velocity. There is no way a projectile angles at 89 degrees to the horizontal will travel further than one 45 degrees to the horizontal

I was just wondering about air resistance, since the values are experiment and the angle with maximum range was like 50 with a concave down parabola on a graoh of the results.  We have to research it and present information for the secondary experiment, and I was wondering how air resistancce affected the theoretical answer

[jamonwindeyer]

I was just wondering about air resistance, since the values are experiment and the angle with maximum range was like 50 with a concave down parabola on a graoh of the results.  We have to research it and present information for the secondary experiment, and I was wondering how air resistancce affected the theoretical answer

This is actually a fairly interesting problem. When we factor in air resistance, we get an additional acceleration in the horizontal direction, opposing the motion. However, do we consider this as a constant acceleration (drag), or is it proportional to the speed of the object itself? It is standard to make the retarding acceleration proportional to the square of the speed, but sometimes we use other functions.

All of this will effect the value of optimum launch angle. Typically we'd obtain something less than 45 degrees, as we need to put a bit more of our velocity into the horizontal component to compensate for the horizontal de-acceleration. If you think about it intuitively, this should make sense. If something is now pushing back against us, it makes sense that we'd want to shoot a bit lower. As another way to think of it, this will reduce the time of flight and thus reduce the amount of time air resistance can slow down the projectile

Definitely not impossible to have 50 degrees as an optimum angle though - It depends on how drag affects the object

[justwannawish]

This is actually a fairly interesting problem. When we factor in air resistance, we get an additional acceleration in the horizontal direction, opposing the motion. However, do we consider this as a constant acceleration (drag), or is it proportional to the speed of the object itself? It is standard to make the retarding acceleration proportional to the square of the speed, but sometimes we use other functions.

All of this will effect the value of optimum launch angle. Typically we'd obtain something less than 45 degrees, as we need to put a bit more of our velocity into the horizontal component to compensate for the horizontal de-acceleration. If you think about it intuitively, this should make sense. If something is now pushing back against us, it makes sense that we'd want to shoot a bit lower. As another way to think of it, this will reduce the time of flight and thus reduce the amount of time air resistance can slow down the projectile

Definitely not impossible to have 50 degrees as an optimum angle though - It depends on how drag affects the object

Then do you think i should say it opposed the theory of 45 degrees being the optimal launch angle?

Also, if you have three trials and get values of say 50, 52, 56, is the 56 an outlier? Should it be excluded when averaging the results?

Thank you once again

[jamonwindeyer]

Then do you think i should say it opposed the theory of 45 degrees being the optimal launch angle?

Also, if you have three trials and get values of say 50, 52, 56, is the 56 an outlier? Should it be excluded when averaging the results?

Thank you once again

I would say it "appears to contradict," then give an explanation as to why. Ultimately the textbook theory is still valid when air resistance is minimal

Mathematically, the 56 isn't an outlier, especially with only three data points. You'd want to include it unless there is a good reason not to (EG - a significant experimental flaw with that trial)

[justwannawish]

I would say it "appears to contradict," then give an explanation as to why. Ultimately the textbook theory is still valid when air resistance is minimal

Mathematically, the 56 isn't an outlier, especially with only three data points. You'd want to include it unless there is a good reason not to (EG - a significant experimental flaw with that trial)

Thank you! Could you also help me compare the theory (and theoretical value) with the actual value of 50 degrees? A scaffold or anything would be great

Also if the qualitative trend is a parabola, what is the quantitative trend?

[justwannawish]

Thank you! Could you also help me compare the theory (and theoretical value) with the actual value of 50 degrees? A scaffold or anything would be great

Also if the qualitative trend is a parabola, what is the quantitative trend?

Hey guys could anyone help me with this question, I'm so sorry for being a bother!

[jamonwindeyer]

Thank you! Could you also help me compare the theory (and theoretical value) with the actual value of 50 degrees? A scaffold or anything would be great

Also if the qualitative trend is a parabola, what is the quantitative trend?

Hey guys could anyone help me with this question, I'm so sorry for being a bother!

No bother! I don't know how I missed it the first time

To compare the two, I think you'd basically just give the two values and explain why they are different. How does the theoretical value come to be, and what does the theory ignore that causes the difference? No scaffold for how or in what order, but that is vaguely what you'd cover.

Qualitative data you really can't link to just a graph, because you can't graph a qualitative trend. Maybe even just one variable goes up while the other goes up, or one goes down while the other goes up?

[justwannawish]

No bother! I don't know how I missed it the first time

To compare the two, I think you'd basically just give the two values and explain why they are different. How does the theoretical value come to be, and what does the theory ignore that causes the difference? No scaffold for how or in what order, but that is vaguely what you'd cover.

Qualitative data you really can't link to just a graph, because you can't graph a qualitative trend. Maybe even just one variable goes up while the other goes up, or one goes down while the other goes up?

Okay thank you!

Also, does performing an experiment outside on different days make it invalid if the results are still consistent? When factoring wind speeds, humidity and stuff like that? e.g. with the pendulum experiment, wouldn't vibrations affect the period of the pendulum, making it invalid?

[Mate2425]

Hi could someone please help me with "what are the features of the Kennedy Space Center which makes it an effective launch site".
Thank you.

[jamonwindeyer]

Okay thank you!

Also, does performing an experiment outside on different days make it invalid if the results are still consistent? When factoring wind speeds, humidity and stuff like that? e.g. with the pendulum experiment, wouldn't vibrations affect the period of the pendulum, making it invalid?

It lessens the validity if those variables would be a factor in the experiment, yes! But it is your judgement as to how much

Hi could someone please help me with "what are the features of the Kennedy Space Center which makes it an effective launch site".
Thank you.

Primarily (would love to hear other ideas) it is located about as close to the equator as it can be within mainland America! Being close to the equator allows the earths rotational motion to be maximised to its fullest extent

[Mate2425]

Ok, thank you

It lessens the validity if those variables would be a factor in the experiment, yes! But it is your judgement as to how much

Primarily (would love to hear other ideas) it is located about as close to the equator as it can be within mainland America! Being close to the equator allows the earths rotational motion to be maximised to its fullest extent