Mathematics: Post your doubts here!

[Haya Ahmed]

Hey Guys, can someone please solve 6 (ii)?

 

[hizirofaki]

Hey Guys, can someone please solve 6 (ii)?

i need help iin this too

 

[DaniyalK]

Hey Guys, can someone please solve 6 (ii)?

there are 2 cases of constant acceleration.
Before reaching the liquid:
a = 10 s = 5 u = o v = ? t = ?
use constant acceleration formulas to find v and t
v = 10, t = 1

Inside the liquid:
a = 5.5 s = 4 u = 10 (v of previous) v = ? t = ?
again use constant acceleration formulas
v = 12, t = 0.36

For the sketch, make a straight line from the origin to (1, 10). This is for the part before the liquid
Then make a line of less gradient from (1,10) to (1.36, 12) for the part inside the liquid.

 

[farhan141]

Why isn't T2 20s? My values were 10 and 30 but when I inserted value of 21 in second derivative of velocity it was giving me positive so increasing? And when I put 19 it was giving me negative so decreasing?

 

[Haya Ahmed]

there are 2 cases of constant acceleration.
Before reaching the liquid:
a = 10 s = 5 u = o v = ? t = ?
use constant acceleration formulas to find v and t
v = 10, t = 1

Inside the liquid:
a = 5.5 s = 4 u = 10 (v of previous) v = ? t = ?
again use constant acceleration formulas
v = 12, t = 0.36

For the sketch, make a straight line from the origin to (1, 10). This is for the part before the liquid
Then make a line of less gradient from (1,10) to (1.36, 12) for the part inside the liquid.

Aren't we supposed to make the graph in the negative section? because it is going downwards isn't it?

 

[DaniyalK]

Aren't we supposed to make the graph in the negative section? because it is going downwards isn't it?

It doesn't matter. You can take any direction as positive as long as the other direction is considered negative.

 

[hizirofaki]

Hey Guys, can someone please solve 6 (ii)?

can u plz draw the graph

 

[Haya Ahmed]

It doesn't matter. You can take any direction as positive as long as the other direction is considered negative.

Won't they cut marks if I drew it in the wrong direction?

 

[farhan141]

Aren't we supposed to make the graph in the negative section? because it is going downwards isn't it?

No it will be downwards if it had bounced off (Part after bouncing will be taken as downward). In this case it is only moving in one direction

 

[farhan141]

It doesn't matter. You can take any direction as positive as long as the other direction is considered negative.

Do u know how to convert a velocity time graph to distance time or vice versa? I'm rly facing issue in this

 

[Haya Ahmed]

No it will be downwards if it had bounced off (Part after bouncing will be taken as downward). In this case it is only moving in one direction

It doesn't matter. You can take any direction as positive as long as the other direction is considered negative.

okay what if the ball was for example projected upwards how will the graph look like?

 

[TheJDOG]

Even if passing through a pulley and it goes to some other angle?

Yes, if the pulley is smooth , it is the same string so same tension

 

[Haya Ahmed]

Why isn't T2 20s? My values were 10 and 30 but when I inserted value of 21 in second derivative of velocity it was giving me positive so increasing? And when I put 19 it was giving me negative so decreasing?View attachment 53464

which year is this ?

 

[farhan141]

Yes, if the pulley is smooth , it is the same string so same tension

Thanks bro

which year is this ?

Oct 2010

 

[hizirofaki]

Yes, if the pulley is smooth , it is the same string so same tension

can u draw the graph

 

[farhan141]

okay what if the ball was for example projected upwards how will the graph look like?

Also upward.

It will only move toward downward/negative side if the ball is moving in 2 directions

 

[farhan141]

Why isn't T2 20s? My values were 10 and 30 but when I inserted value of 21 in second derivative of velocity it was giving me positive so increasing? And when I put 19 it was giving me negative so decreasing?View attachment 53464

I have some doubts please clear.

- Why is 'c' ignored when integrating velocity to find disp?

 

[DaniyalK]

Do u know how to convert a velocity time graph to distance time or vice versa? I'm rly facing issue in this

It's not too bad as long as you understand that the v/t graph is the graph of the gradient of s/t and remember a few cases.
constant velocity is a straight diagonal line for displacement
straight diagonal line for velocity is increasing gradient graph for displacement
curved graph for velocity is increasing gradient at an increasing/decreasing rate for displacement, depending on the curve in the v/t graph

I have some doubts please clear.

- Why is 'c' ignored when integrating velocity to find disp?

Because we are doing definite integration. The c cancels out.

Won't they cut marks if I drew it in the wrong direction?

There is no 'right' or 'wrong' direction. Positive can be any direction as long as you show motion in the opposite direction as negative.

 

[hizirofaki]

I have some doubts please clear.

- Why is 'c' ignored when integrating velocity to find disp?

becuase u r integraing with ''limits'
can u help me why did we take a=0 t find t1 ?

 

[Haya Ahmed]

I have some doubts please clear.

- Why is 'c' ignored when integrating velocity to find disp?

Because "S" is zero when "t" is 0 so "C" is zero and it gets cancelled