HSC Physics Question Thread

[justwannawish]

Seems the mass of the atmosphere is about \(5\times10^{18}\text{kg}\), give or take, so that would be inconsequential compared to the mass of the earth - Kind of like taking your earphones out before getting on the scales maybe

Yep, that makes sense. another question, sorry, I'm just trying to learn space before school does so it makes sense to me
Is the acceleration at the top of a point (maximum height) 0 or -9.8? Because what I'm currently understanding is that  the vertical velocity be 0 as well, so would the acceleration would be 0 as well??

Btw, bought the atarnotes practice papers book and it's looking great

[jamonwindeyer]

Yep, that makes sense. another question, sorry, I'm just trying to learn space before school does so it makes sense to me
Is the acceleration at the top of a point (maximum height) 0 or -9.8? Because what I'm currently understanding is that  the vertical velocity be 0 as well, so would the acceleration would be 0 as well??

Btw, bought the atarnotes practice papers book and it's looking great

All good! Good on you for getting ahead

The vertical acceleration is constant, \(-9.8\text{m/s}^2\) - Doesn't matter what point in the motion you are at, that is always the value

So glad you are liking the topic tests

[sidzeman]

Yep, that makes sense. another question, sorry, I'm just trying to learn space before school does so it makes sense to me
Is the acceleration at the top of a point (maximum height) 0 or -9.8? Because what I'm currently understanding is that  the vertical velocity be 0 as well, so would the acceleration would be 0 as well??

Btw, bought the atarnotes practice papers book and it's looking great

No, acceleration towards the centre of the Earth remains constant at 9.8 (or -9.8 ) during the entirety of the projectiles motion.

[sidzeman]

Question - do geostationary satellites not experience orbital decay?

[clarence.harre]

Please help with this Multiple Choice question from the 2016 paper.

Q11: What is the wavelength, in metres, of a photon with an energy of 3.5eV?
Working:
3.5 * 1.602*10^-19 = 5.607*10^-19 Joules
Since E = hc/λ,
then   λ = hc/E

Therefore, λ = hc/(5.607*10^-19)
                    = 3.54 * 10^-7
This corresponds with option B, but the answer is C, i.e. λ = 1.18 * 10^-15

[justwannawish]

All good! Good on you for getting ahead

The vertical acceleration is constant, \(-9.8\text{m/s}^2\) - Doesn't matter what point in the motion you are at, that is always the value

So glad you are liking the topic tests

No, acceleration towards the centre of the Earth remains constant at 9.8 (or -9.8 ) during the entirety of the projectiles motion.

Okay, thank you guys. Will probably be back with many more questions soon! But a huge thank you to the community here for answering them

[itssona]

hiii lil question from space module,, thank you

the gravitational field vector g has an average value on the surface of earth, of 9.8Nkg^-1 or ms^-2. Show that the two alternative units quoted are equivalent

[Shadowxo]

hiii lil question from space module,, thank you

the gravitational field vector g has an average value on the surface of earth, of 9.8Nkg^-1 or ms^-2. Show that the two alternative units quoted are equivalent

So 1N = 1kg.ms^-2 (F=ma)
Hence Nkg^-1=kgms^-2kg^-1=ms^-2

[itssona]

So 1N = 1kg.ms^-2 (F=ma)
Hence Nkg^-1=kgms^-2kg^-1=ms^-2

thank you Shadow

[itssona]

sorry for coming again buuut, having trouble understanding how earth's rotation affects g?

my textbook talked about how earth would actually needto rotate every 20 seconds in order for objects to fling off the surface.. but i dont get where theyre going at?

also is thrust of a rocket basically its initial force, so Net Force PLUS weight since it has to overcome gravity?

thank you so muchhh

[pikachu975]

sorry for coming again buuut, having trouble understanding how earth's rotation affects g?

my textbook talked about how earth would actually needto rotate every 20 seconds in order for objects to fling off the surface.. but i dont get where theyre going at?

also is thrust of a rocket basically its initial force, so Net Force PLUS weight since it has to overcome gravity?

thank you so muchhh

Earth's rotation creates a centrifugal force that goes outwards, which reduces the EFFECTIVE VALUE of g.

Thrust = mv I think (can someone pls confirm) but using the formula, am = T - mg, T = F + mg so yes you're correct

[itssona]

Earth's rotation creates a centrifugal force that goes outwards, which reduces the EFFECTIVE VALUE of g.

Thrust = mv I think (can someone pls confirm) but using the formula, am = T - mg, T = F + mg so yes you're correct

ohh makes sense now, thank youuu

[jamonwindeyer]

Question - do geostationary satellites not experience orbital decay?

Nope - Well, a negligible amount at least

Please help with this Multiple Choice question from the 2016 paper.

Q11: What is the wavelength, in metres, of a photon with an energy of 3.5eV?
Working:
3.5 * 1.602*10^-19 = 5.607*10^-19 Joules
Since E = hc/λ,
then   λ = hc/E

Therefore, λ = hc/(5.607*10^-19)
                    = 3.54 * 10^-7
This corresponds with option B, but the answer is C, i.e. λ = 1.18 * 10^-15

I also get B when I calculate! Perhaps it's an error in the supplied solutions? (happy for someone to correct me!)

[pikachu975]

Please help with this Multiple Choice question from the 2016 paper.

Q11: What is the wavelength, in metres, of a photon with an energy of 3.5eV?
Working:
3.5 * 1.602*10^-19 = 5.607*10^-19 Joules
Since E = hc/λ,
then   λ = hc/E

Therefore, λ = hc/(5.607*10^-19)
                    = 3.54 * 10^-7
This corresponds with option B, but the answer is C, i.e. λ = 1.18 * 10^-15

HSC answers have B, maybe you looked at the wrong one!

[itssona]

anyone know how galileo's analysis of projectile motion showed evidence to support his heliocentric model?