can someone explain this velocity-time graph for me (1 Viewer)

[Shavi Masee]

Why is the ball decelerating as it goes up in the first second?? Is it because of air resistance?

 

[C2H6O]

View attachment 46514
Why is the ball decelerating as it goes up in the first second?? Is it because of air resistance?

Bc gravity is the only force (in HSC phys) that acts on projectiles such as balls. You'll learn more in mod 5 but for now just know that any ball thrown is always being pulled down by gravity. Think about when you throw a ball straight up, it slows down and evenually stops and changes direction and then speeds toward the ground. Acceleration is constant downwards. If it was positive (up) at any point that would mean the ball is speeding up while gaining altitude, which is not possible.

 

[Shavi Masee]

Bc gravity is the only force (in HSC phys) that acts on projectiles such as balls. You'll learn more in mod 5 but for now just know that any ball thrown is always being pulled down by gravity. Think about when you throw a ball straight up, it slows down and evenually stops and changes direction and then speeds toward the ground. Acceleration is constant downwards. If it was positive (up) at any point that would mean the ball is speeding up while gaining altitude, which is not possible.

so this only happens to the graph if the ball is moving upward?
If something is moving straight (left or right) then it would look like it's accelerating then? (in the direction specified in the graph) But even if it's decelerating the graph can never go in the negative velocity?

 

[C2H6O]

so this only happens to the graph if the ball is moving upward?
If something is moving straight (left or right) then it would look like it's accelerating then? (in the direction specified in the graph) But even if it's decelerating the graph can never go in the negative velocity?

Yeah basically. whenever youre dealing with up down motion you assume there's gravity unless specified. In horizontal motion there would be other forces involved. So if this velocity time graph was horizontal, and right is positive, then it would apply to like a cart or something that is moving to the right and braking, and when it stops it starts reversing faster and faster toward the left.

Also anytime the v-t graph is not just a horizontal line that means theres acceleration (change in velocity)

 

[C2H6O]

But even if it's decelerating the graph can never go in the negative velocity?

Negative velocity just means the opposite direction of what you've assigned as positive. Typically its UP (+), RIGHT (+), DOWN (-), LEFT(-), but you can change it to whatever fits the question, just make sure opposite directions are opposite in sign

 

[Shavi Masee]

So if this velocity time graph was horizontal, and right is positive, then it would apply to like a cart or something that is moving to the right and braking, and when it stops it starts reversing faster and faster toward the left.

sry but why is it moving "faster and faster to the left"? is it not moving to the right at the same velocity?


ohh wait nvm it's slowing down toward the right T-T
Thank you so much for explaining, i couldn't wrap my head around it and I thought it was important to know!

 

[C2H6O]

sry but why is it moving "faster and faster to the left"? is it not moving to the right at the same velocity?


ohh wait nvm it's slowing down toward the right T-T

I was mentioning the negative part of the graph. I hope this image makes it clearer. BTW these annotations apply to a cart moving HORIZONTALLY with right assigned as the positive direction.

 

[C2H6O]

sry but why is it moving "faster and faster to the left"? is it not moving to the right at the same velocity?


ohh wait nvm it's slowing down toward the right T-T
Thank you so much for explaining, i couldn't wrap my head around it and I thought it was important to know!

All g its important to understand this its definitely hard to understand this when starting out physics dw

 

[Shavi Masee]

View attachment 46516
I was mentioning the negative part of the graph. I hope this image makes it clearer. BTW these annotations apply to a cart moving HORIZONTALLY with right assigned as the positive direction.

YOUR EXPLAINING IS SO GOOD

 

[coolcat6778]

View attachment 46514
Why is the ball decelerating as it goes up in the first second?? Is it because of air resistance?

because its accelerating downwards at 10 m/s^2 which can be seen by the gradient of the graph dv/dt which = acceleration