Physics: Post your doubts here!

[Thought blocker]

can you please tell me how you got that

He has mentioned all things in detail, where are you stuck?
In summary, get t from vertical motion (VM) and horizontal distance from horizontal motion (HM) using the time values you got in VM. That's it, use your calculator properly.

 

[Glory Hunter]

He has mentioned all things in detail, where are you stuck?
In summary, get t from vertical motion (VM) and horizontal distance from horizontal motion (HM) using the time values you got in VM. That's it, use your calculator properly.

i got it thanx

 

[Thought blocker]

i got it thanx

 

[Glory Hunter]

in first question what do he mean by this
Since water is shot from horizontal pipe, it has no vertical component of velocity.

 

[Thought blocker]

in first question what do he mean by this
Since water is shot from horizontal pipe, it has no vertical component of velocity.

He meant, coz water is shot out from horizontal pipe, Vertical component of initial velocity, u = 0.

 

[Glory Hunter]

He meant, coz water is shot out from horizontal pipe, Vertical component of initial velocity, u = 0.

Ohok

 

[Glory Hunter]

I have added some more details there.

Please tell me the answers given in the book for all 3 questions (7,8,9) so that i can check whether my work is correct

Ok I well tell thanx for helping

 

[Glory Hunter]

I have added some more details there.

Please tell me the answers given in the book for all 3 questions (7,8,9) so that i can check whether my work is correct

thanx for the more info and yes the answers where right thanx a lot

 

[janasalem]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s12_qp_23.pdf

question 1 c(ii)
can someone draw this and send a photo and how to find the magnitudes from the vector triangle?

 

[Tan Zhao Xuan]

t

Tan Zhao Xuan
The explanation is available at (at the end)
http://physics-ref.blogspot.com/2014/05/physics-9702-notes-worked-solutions-for.html

you may ask for any of your physics doubts there

thank you. I really appreciate that.

 

[princess Anu]

For the velocity time graph, how do I get the average speed for the entire set of data? It starts at the origin, then goes up to (120,25) for A, and then the final point is F which is (720, -140)

 

[Thought blocker]

For the velocity time graph, how do I get the average speed for the entire set of data? It starts at the origin, then goes up to (120,25) for A, and then the final point is F which is (720, -140)

Average speed is total distance travelled / total time.
If the velocity is always zero or greater then average velocity is the same value.

If the velocity drops below zero then you need to add a couple of steps.

Divide the motion into the four regions.
1. acceleration
2. constant
3 negative acceleration
4. positive acceleration

For each of these regions find two things a) the time spent in the region and b) the average velocity (= (V2 + V1)/2 )


Multiply the time by the average velocity for each section.

Add the four answers to get the total distance

Divide by the total time.

If there is any region where the velocity is negative you would need to treat each of those sections as yet more pieces. In those pieces the DISTANCE is positive and is added on prior to calculating average speed.

 

[princess Anu]

A tennis player standing 5.5m from the net. she hits the ball horizontally at a speed of 32ms. How far has the ball dropped when it reaches the net? take g=10

Can we use v^2= u^2 + 2as to solve this?

 

[Thought blocker]

A tennis player standing 5.5m from the net. she hits the ball horizontally at a speed of 32ms. How far has the ball dropped when it reaches the net? take g=10

Can we use v^2= u^2 + 2as to solve this?

What is the answer?
0.15m?

 

[princess Anu]

If there is any region where the velocity is negative you would need to treat each of those sections as yet more pieces. In those pieces the DISTANCE is positive and is added on prior to calculating average speed.[/QUOTE]

Yes the answer is 0.15m
Btw If we have to find average velocity, the displacement will be -ve in those regions of the section where velocity is below zero, right?

 

[Thought blocker]

If there is any region where the velocity is negative you would need to treat each of those sections as yet more pieces. In those pieces the DISTANCE is positive and is added on prior to calculating average speed.

Yes the answer is 0.15m
Btw If we have to find average velocity, the displacement will be -ve in those regions of the section where velocity is below zero, right?[/QUOTE]
Find the time with, t = s/v = 5.5/32 = 0.171875
Then use s = 1/2at^2 = 5*0.171875^2 = 0.15m

The DISPLACEMENT is negative and is subtracted before calculating average velocity.

 

[princess Anu]

why can't we directly use v^2= u^2+2as ?

 

[Thought blocker]

why can't we directly use v^2= u^2+2as ?

I bet you cannot get answer with that equation.
We need time to calculate that distance asked.
SO we used s/v
Use everything given in the question and go according to the format.

 

[princess Anu]

Yea i know But WHYYY
We've got everything except displacement why can't we use this eq

 

[princess Anu]

Yes the answer is 0.15m
Btw If we have to find average velocity, the displacement will be -ve in those regions of the section where velocity is below zero, right?

Find the time with, t = s/v = 5.5/32 = 0.171875
Then use s = 1/2at^2 = 5*0.171875^2 = 0.15m

The DISPLACEMENT is negative and is subtracted before calculating average velocity.[/QUOTE]
The eq u used isn't it incomplete ? where is u*t? initial velocity is not even O in this case?