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HSC Physics Question Thread
Coolmate:
Hi Everyone,
Could someone please step me through how to solve this question (attached) from the 2012 HSC paper (Q27, 2012)
Thanks in advance,
Coolmate 8)
fun_jirachi:
Hey :)
One of the first things that pops out to me is that you have that the horizontal displacement is 45m - indicating that from \(s_x = u_xt\), we have that \(45 = u\cos 60 \times t\). Secondly, we have that from \(s_y = u_yt - \frac{1}{2}gt^2\) - thus we also have that \(34 = u\sin 60 \times t - \frac{gt^2}{2}\). Rearranging and substituting the first equation into the second yields an equation in \(u\), specifically Rearrange and solve from here to get the answer of 30ms-1
The thought process I followed here was to start with the easiest equations that you can substitute info from the question into - it's important to ask yourself what do you know? It's also important to try and eliminate one variable ASAP in equations of multiple variables (you can always sub back in later to find the other once you've found a definitive value for one of them). If all else fails, literally write down everything they give you ie. \(s_x = 45, s_y = 34\) and see what equations 'match up' - much like questions towards the back end of maths exams and stuff (just try something!) Definitely look to practice more of these types of questions (or change the numbers a bit) if this is the type of thing you struggle with :)
Coolmate:
--- Quote from: fun_jirachi on August 24, 2020, 05:44:54 pm ---Hey :)
One of the first things that pops out to me is that you have that the horizontal displacement is 45m - indicating that from \(s_x = u_xt\), we have that \(45 = u\cos 60 \times t\). Secondly, we have that from \(s_y = u_yt - \frac{1}{2}gt^2\) - thus we also have that \(34 = u\sin 60 \times t - \frac{gt^2}{2}\). Rearranging and substituting the first equation into the second yields an equation in \(u\), specifically Rearrange and solve from here to get the answer of 30ms-1
The thought process I followed here was to start with the easiest equations that you can substitute info from the question into - it's important to ask yourself what do you know? It's also important to try and eliminate one variable ASAP in equations of multiple variables (you can always sub back in later to find the other once you've found a definitive value for one of them). If all else fails, literally write down everything they give you ie. \(s_x = 45, s_y = 34\) and see what equations 'match up' - much like questions towards the back end of maths exams and stuff (just try something!) Definitely look to practice more of these types of questions (or change the numbers a bit) if this is the type of thing you struggle with :)
--- End quote ---
Hey fun_jirachi, :)
Thankyou for the assistance, it really helped me today! (I just came out of my Physics Trial exam and your help was very helpful)
Thanks again!
Coolmate 8)
jessica2166:
Can someone help me with this?
The total energy of a satellite is equal to the sum of its gravitational potential energy and its orbital kinetic energy. However, the work done to put that satellite into orbit is less than this.
Explain how this does not contravene the law of conservation of energy.
mrsc:
Hey, just wondering if anyone could recommend the most important practical experiments we are required to know. Thanks
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