VCE Physics Question Thread!

[Syndicate]

Ok, that makes sense. Could you then please explain to me why from a particular height, a ball thrown at a 45 angle will go further than one thrown horizontally, and why a horizontally thrown ball travels further than one thrown at say 30 or 60? Thanks.

Think about the formula: The maximum value sin can possess is 1, which is at 90 degrees. If the ball is thrown at 45 degrees, sin2(angle) will equal to 1. You can try any other angle (upto 90 degrees), and you will always get a lower value than when the angle is 45 degrees.

[Redoxify]

Help plz </3

[Syndicate]

Help plz </3

(a) use the formula of horizontal displacement (to find the time it takes for it to fall 1.46 m):


Therefore:
1.46 = 0+4.9t^2
1.46/4.9 = t^2

t = 0.545856376

Now to find the velocity of the mug falling down the distance 2.2 m, we must divide 2.2 by t (because v = distance/ time)

2.2/t = 4.03 m/s (approximately)

(b) This can be solved by finding the vertical value, and subbing it in the formula:


verticle velocity = sqrt(2g x h) (derived formula)
= 5.35 m/s

[Syndicate]

In class, we're doing this weird identifying errors worksheet as our holiday homework to get us in the right mindset to scrutinise our pracs and better identify errors or whatever. I'm stuck on this question though (found here because the photo was apparently too big of a file: http://uploadpie.com/2eKGy). Basically, we have to find an error and suggest potential ways of resolving it.

We have to come up with five potential sources of error and so far, all I've got is
1. Friction between the board and the trolley rolling down the board. - How would I solve this error? Especially considering we can't exactly tell friction to go get lost so we can do our physics experiment in peace...

2. An inaccurate reading of the distance travelled (because I'm assuming they're measuring the distance with like a ruler)
Errrr.... be more precise about readings?

3. Reaction times? Shorter travel times = shorter time for the person with a stopwatch to react. Could be solved by using some of that fancy gadgetry where the moment the trolley starts rolling, a sensor detects it and starts timing and when it passes the end point, another sensor detects it and stops timing and you get a super exact time. These things do exist, right?

Someone please help me find 2 more errors?

Just saying... errors are not the mistakes you have made in the prac (so errors are the things that are wrong in your method). Your points 2 and 3 are mistakes (the things that can be fixed, if you do the Parc again), and I don't believe they would considered as errors.

[lzxnl]

They still count as experimental errors.

[Syndicate]

Bump. Anyone? Pretty pleaseeee?

A few things I came up with:

- stability of the track over different angles
- the force applied when the trolley was released (by the person)- this can cause inaccuracies
- At the end, the trolley was slowed down due to a sudden bump

[Syndicate]

What do you mean by the first point?

I mean that was the track stable enough to allow the trolley car to accelerate down it easily. Was the track moving? shaking? etc.. (I have done this experiment before, and we used wooden planks to make the track, so it was a little shaky at a higher angle).

[knightrider]

For a pendulum EPI.

say your variable was angles . What formulas could you use to work out the angles?

Also what would be some other good variables to investigate relating to the  pendulum EPI ?

[Syndicate]

Ohhh. Thanks Syndicate. I only just saw this.

For that inclined plane experiment with the cart rolling down the plane, is there any way we can account for friction? Is there any way to figure out the amount of friction acting?

Generally, most of the motion formulas used in VCE Physics tend to ignore friction. I don't think you can calculate friction, as there isn't enough information given, however, you can say that the friction was not 'stronger' than the trolley car's acceleration, as it was able to move (whereas, if it wasn't able to move, then it would have meant that friction was stronger than the force applied to the trolley car).  So yeah... you shouldn't really worry about it.

For a pendulum EPI.

say your variable was angles . What formulas could you use to work out the angles?

I am not quite sure about the formula, however, I did a little research and found this great website (it has some good information)- https://www.boundless.com/physics/textbooks/boundless-physics-textbook/waves-and-vibrations-15/periodic-motion-123/the-simple-pendulum-431-8324/

hopefully others will be able to help you here 

Also what would be some other good variables to investigate relating to the  pendulum EPI ?

- length of the pendullum (does it increases/decreases it's velocity?)- l (length variable)
- mass of bob (again, what effects does it have on the velocity)- m (mass of bob)

[Syndicate]

Then how would we solve the source of error that is friction for this experiment? All of our equations assume ideal-ness but obviously there is no such thing as an ideal situation so how would you be able to calculate an acceleration similar to the theoretical acceleration if the friction was present? Wouldnt you end up with a huge experimental error because of friction which we did not take into consideration?

Friction is an error because it's causing a change in the trolley's speed, and we know that friction is not accounted for when solving for speed. You are absolutely correct about your last point, as if you were to measure the trolley's final speed with hi-tech equipment, you would end up with something completely different compared to what you worked out on your piece of paper. We cannot completely remove friction, so maybe your answer to this question can be using a track with a surface producing minimal friction.

[knightrider]

I am not quite sure about the formula, however, I did a little research and found this great website (it has some good information)- https://www.boundless.com/physics/textbooks/boundless-physics-textbook/waves-and-vibrations-15/periodic-motion-123/the-simple-pendulum-431-8324/

hopefully others will be able to help you here 

- length of the pendullum (does it increases/decreases it's velocity?)- l (length variable)
- mass of bob (again, what effects does it have on the velocity)- m (mass of bob)

Thanks Syndicate 

[YellowTongue]

If a mass follows a circular trajectory in a vertical plane, will increasing the size of the mass or radius of motion change the period of motion or the minimum speed that the mass can travel at?

[Peanut Butter]

If a mass follows a circular trajectory in a vertical plane, will increasing the size of the mass or radius of motion change the period of motion or the minimum speed that the mass can travel at?

minimum speed = root(r x g)

Hence, changing the radius will affect the minimum speed however changing the mass will not make a difference 😊

[Edge_of_Chaos]

A basketball player jumps directly upwards so that his centre of mass reaches a maximum displacement of 50 cm.

A) What is the velocity of the basketballs centre of mass when it returns to its original height above the ground?

B) For how long was the basketballs centre of mass above its original height?

[lzxnl]

A basketball player jumps directly upwards so that his centre of mass reaches a maximum displacement of 50 cm.

A) What is the velocity of the basketballs centre of mass when it returns to its original height above the ground?

B) For how long was the basketballs centre of mass above its original height?

This is a 1 D gravitational motion question. The centre of mass bit is a more accurate way of saying the basketball player moved up 50 cm (because then you have the problem of what part of their body moved up 50 cm). Does that help?