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#### ashmi

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##### Physics - Test Your Understanding
« on: April 28, 2020, 04:31:30 pm »
+13

Huge shoutout to J_Rho for suggesting a Physics thread too! (Go Physics gang! )

Every week on Monday, a handful of questions on a topic will be posted to help you revise, consolidate knowledge and help each other out! You can post your answers for feedback, as well as having the opportunity to give others feedback! (If you want to post anon you can PM me or any other member to post them for you)

This week we are going to be testing our knowledge of 'Newton's laws of motion', which is the first 5 dot points of the study design! AOS 3 (Excluding one on satellites which can come later).

Week 1: 'Newton's laws of motion'
*If these questions are too easy/hard, please let me know so I can try adjusting them accordingly. (Also, there are some original questions on here and it would be great if there is no reposting of them)*

Q1. Two physics students are conducting accurate experiments to test Newton’s second law of motion (ΣF = ma). Each student is in a windowless railway carriage. One carriage (carriage A) is moving at a constant velocity of 0.9c. The other carriage (carriage B) is moving at 10 m s–1 and decelerating. Which one of the following best describes the likely results of their experiments?

A. Only the experiment in carriage A confirms Newton’s second law of motion.
B. Only the experiment in carriage B confirms Newton’s second law of motion.
C. Neither experiment confirms Newton’s second law of motion.
D. Both experiments confirm Newton’s second law of motion.
[VCAA 2010 EXAM 1, Q5: Einstein's Special Relativity]

Q2. A student drops a tennis ball from a 20m high building and 0.60s later, she throws a basketball with an initial velocity of 8m/s.  How long will it take for the basketball to pass the tennis ball?

[HSC 1980 Q3, 1 mark]

Q3. A ball is thrown from a cliff with the initial velocity of 25ms-1. What is the ball's location and velocity after 3.00 seconds? (Neglect the size of the person throwing the ball.) Answer using coordinates (x,y) and ms-1.
A diagram is provided for your reference:

[Original Question]

Q4. A block of wood, with a piece of putty attached (total mass M1) is travelling at a constant speed U over a frictionless surface. It strikes a second block (M2) and the two move off together with an initial velocity V and initial kinetic energy K. The blocks are subjected to a constant frictional force F, and come to rest after travelling a distance d.

Which of the following expressions relating to the kinetic energy of the system is correct?
A.    ½M1U2 = Fd
B.    ½M1U2 = ½(M1 + M2)V2
C.    ½M1U2 > Fd
D.    ½(M1 + M2)V2 - ½M1U2 = Fd
E.    ½(M1 + M2)V2 > Fd

[HSC 1982 Q11, 1 mark]

Q5. A local amusement park decides to copy a ride from another popular theme park. The new "cupcake ride" is inspired by an original circular ride which when someone travels at a fast enough speed, they will not slide down the wall. The new design is below the first diagram. A person with a mass of 60kg decides to test out a prototype of this ride. Assuming there is no friction, what is the minimum speed in ms-1 needed so the person doesn't slide down? (Note: The blue line is exactly in the centre of the person. Also, the first diagram is the one they copied from the theme part and the second diagram is the official prototype)

[Original Question. Thank you Collin Hopkin's Notes for the inspiration!]

Q6.
A motorcycle travels around a vertical circular path of radius 3.6 m at a constant speed. The combined mass of the rider and motorcycle is 200 kg.

What is the minimum speed, in m s–1, at which the motorcycle must travel to maintain the circular path?
A.    0.42
B.    1.9
C.    5.9
D.    35

[2016 NSW Question 18, 1 mark]

Solutions will be updated later but I would really love you all to give it a go and reply with your responses! If you would like to contribute, please do!
« Last Edit: May 18, 2020, 05:51:15 pm by ashmi »
VCE
2019: Further [44]
2020: Methods | PDT | Chemistry | Physics | English

KLD 2020
"It is a mere puzzle, solve it"

☆The CASual Journey to the End | Ashmi's VCE Journal☆
☆Further Maths | Guide☆
Have some fun with Physics!
NYSF
Duke of Ed

#### ArtyDreams

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##### Re: Physics - Test Your Understanding
« Reply #1 on: April 28, 2020, 04:36:12 pm »
+7
Super excited for this!

Will update with some more questions later this week.
the world is too heavy to carry alone.

VCE Class of 2020

My Short Guide to Mathematical Methods
Study Motivation Tips

#### ashmi

• MOTM: June 20
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##### Re: Physics - Test Your Understanding
« Reply #2 on: May 03, 2020, 06:30:53 pm »
+9
Hello Physics Gang

Here are the answers to the first batch of Physics Questions on "Newton's Law of Motion"

Question 1
Q1) A
Since the carriage is windowless, there is no possible way to confirm in carriage B if someone is decelerating or if there is an outside force pushing on the carriage. Carriage A on the other hand is at a constant velocity, meaning that someone inside the carriage wouldn't feel any difference, thus being able to confirm Newton's second law.
Question 2
Q2) 1.43 seconds
We know when the basketball passes the tennis ball, they need to cover the same total distance, thus we can make a simultaneous equation with:
$s= ut+\frac{1}{2}at^{2}$
$0\times t+\frac{1}{2}\times 9.8\times t^{2} = 8\times(t-0.6)+\frac{1}{2}\times 9.8\times (t-0.6)^{2}$
t = 1.43 seconds
Question 3
Q3) Coordinates from origin (37.5, 20.9) and velocity is 14.71m/s and is 38.1 degrees from horizontal.

Find horizontal first: $25\times cos(60) \times 3 = 37.5m$
Find Vertical: $s= ut+\frac{1}{2}at^{2}$
$s= 25\times sin(60) \times 3 +\frac{1}{2}\times -9.8 \times 3^{2}$
s = 20.9m
Coordinates are (37.5, 20.9)

Velocity:
$v = u + at$
$v = 25 \times sin(60) + -9.8 \times 3$
v = -7.75m/s
Add vector, Horizontal and Vectical with Pythagoras.
√((12.5)^2+(7.75)^2 )
= 14.71 m/s down and 31.8 degrees from horizontal. (Tan-1 (7.75/12.))
Question 4
One thing to note in this problem, is that there is a constant frictional force, meaning that the KE is not 100% conserved in comparison to the start of the problem.
In the top diagram, the KE is 1/2mv^2, however, in the diagram below, there is also a frictional force and 1/2(m1+m2)v^2
An expression for this can be:
$\frac{1}{2}m_{1}v_{1}^{2}= \frac{1}{2}(m_{1}+m_{2})v_{2}^{2} + Fd$

Looking at the options available, the only correct answer is C.
Question 5
Solve Vectors

Question 6
$v = \sqrt{gr}$
$v = \sqrt{9.8\times 3.6}$

Stick around for more soon~
VCE
2019: Further [44]
2020: Methods | PDT | Chemistry | Physics | English

KLD 2020
"It is a mere puzzle, solve it"

☆The CASual Journey to the End | Ashmi's VCE Journal☆
☆Further Maths | Guide☆
Have some fun with Physics!
NYSF
Duke of Ed

#### ArtyDreams

• MOTM: Jan 20
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• Posts: 329
• Fly against the wind. Not with it.
• Respect: +396
##### Re: Physics - Test Your Understanding
« Reply #3 on: May 05, 2020, 06:04:52 pm »
+6
A new set of questions!

This week we are going to be testing our knowledge of Force and Energy, which is the first 3 dot points under ‘Force, Energy and Mass,' (in AOS3 - How fast can things go?)

Week 2: Forces & Energy

Q1a.A boy with a mass of 80kg is running at a speed of 4m/s as he steps onto a stationery trolley of mass 40kg as shown in figure 1. He holds onto the trolley. They then move together in the same direction. What is the speed of the trolley as soon as he gets on board? [2marks]

Q1b.Is this an elastic or inelastic collision? Justify your answer with a calculation. [3marks]

[VCAA 2009 Q1,2]

Q2.A tow truck applies a horizontal force of 3000 N on a 2000 kg car for a period of three seconds over a distance of 20 m.
Calculate the work done by the tow truck over the 20m distance. [2 marks]

[Original Question]

Q3a.Theres an ideal spring with a spring of mass 2kg attached. It is initially held at rest so the spring is not extended. The mass is gently lowered and the spring stretches until the spring mass system is at rest. The spring has extended by 0.40m.
What is the value of the spring constant of the spring? [2marks]

Q3b.What is the difference in the magnitude of the total energy of the spring mass system before and after it is extended? [2marks]

[VCAA 2010, Q13,14]

Q4What does the area under a force-distance graph represent? [1 mark]

[Original Question]

The answers will be posted on Friday in this post, to allow everyone time to have a go and give and get feedback!
the world is too heavy to carry alone.

VCE Class of 2020

My Short Guide to Mathematical Methods
Study Motivation Tips