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Physics: Circular Motion

My answer was B, but that's incorrect.
Can anyone help me out?
Annotation 2020-07-16 123124.png
It is A lol. Distance is greater than 0 but when it returns to the same spot the displacement would be 0. Okay?
Original post by bored_user:)
It is A lol. Distance is greater than 0 but when it returns to the same spot the displacement would be 0. Okay?

Incorrect.

Original post by LeLivre
My answer was B, but that's incorrect.
Can anyone help me out?
Annotation 2020-07-16 123124.png

You know the angular velocity - pi/2 (rad/s)
You know the time - 6 (seconds)

Using your knowledge about how many radians are in a circle, workout how long it will take to complete a whole turn, then work out how much further it will travel in the time remaining
Original post by Becca216
Incorrect.


You know the angular velocity - pi/2 (rad/s)
You know the time - 6 (seconds)

Using your knowledge about how many radians are in a circle, workout how long it will take to complete a whole turn, then work out how much further it will travel in the time remaining

I missed the 6 seconds lol. I hate my life lmaooo
Reply 4
Avatar for LeLivre
LeLivre
OP
10
Original post by Becca216
Incorrect.


You know the angular velocity - pi/2 (rad/s)
You know the time - 6 (seconds)

Using your knowledge about how many radians are in a circle, workout how long it will take to complete a whole turn, then work out how much further it will travel in the time remaining

I found that the time period is 4 seconds using w= 2pi/T
However, my answer always ends up as 2.4pi or 0.8pi
I'm using (2pi)rt/T
Original post by LeLivre
I found that the time period is 4 seconds using w= 2pi/T
However, my answer always ends up as 2.4pi or 0.8pi
I'm using (2pi)rt/T

So, you know that if the time period is 4, then in 6 seconds 1 and 1/2 cycles are completed. Now 1/2 a cycle = pi = 180 degrees, or in other words a straight line.

You know the radius so if the car ends up exactly opposite then you can work out the displacement.

It is a bit of a tricky question when you first look at it, but the easiest way to solve it is not by using equations but by using a bit of logic and problem solving :smile:
Reply 6
Avatar for LeLivre
LeLivre
OP
10
Original post by Becca216
So, you know that if the time period is 4, then in 6 seconds 1 and 1/2 cycles are completed. Now 1/2 a cycle = pi = 180 degrees, or in other words a straight line.

You know the radius so if the car ends up exactly opposite then you can work out the displacement.

It is a bit of a tricky question when you first look at it, but the easiest way to solve it is not by using equations but by using a bit of logic and problem solving :smile:

I worked out the circumference of the semicircle but I still get 0.8pi but the circumference of the entire circle gives me 1.6pi
Sorry I'm very confused
Original post by LeLivre
I worked out the circumference of the semicircle but I still get 0.8pi but the circumference of the entire circle gives me 1.6pi
Sorry I'm very confused

You don't need to work out the circumference - the displacement is not the route it took but the most direct 'line' from where it started to where it finished - in this case that would be the diameter.

Hope that makes some kind of sense :smile:
Reply 8
Avatar for LeLivre
LeLivre
OP
10
Original post by Becca216
You don't need to work out the circumference - the displacement is not the route it took but the most direct 'line' from where it started to where it finished - in this case that would be the diameter.

Hope that makes some kind of sense :smile:

Oh thank you so much! That makes a lot of sense!
So would the answer be C?
So sorry for wasting your time...
(edited 3 years ago)
Yes it would and no worries :smile:

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