Kinematics - Motion Graphs

[Usman17]

Hey Guyz... I am extremely confused about the words I need to use when describing the motion in velocity time graphs :%) ... How to define acceleration nd velocity :| Can some1 please explain

 

[CaptainDanger]

Have you checked the Physics Classroom website for it?

 

[abcde]

Acceleration: Rate of change of velocity with time.
Velocity: Rate of change of displacement with time.
Remember for distance-time graphs, you have to describe how distance changes (increases or decreases, uniformly or non-uniformly) with time. You must also describe speed (constant or increasing/decreasing).
For speed-time graphs, you have to describe both speed and acceleration.

 

[Usman17]

I did but they also didnt make any sense to me :|

 

[abcde]

@Usman: post questions here and I'll describe the graphs for you. Doing examples can help.

 

[Usman17]

@abcde: dude i know these things... I am asking for the appropraite words to describe the graphs... whether we have to write about gradient or wat... :O

 

[abcde]

Oh, I'm sorry. We don't usually mention gradient. Such questions are usually 2 mark ones. Each graph has its own description so I can help you if you put an example here...

 

[Usman17]

ohk wait...

 

[Usman17]

BINGO http://www.xtremepapers.me/CIE/Cambridg ... 3_qp_2.pdf
1st question in detail

 

[Usman17]

I will tell you how i wud have written this:
a) the speed of the lorry increases and then becomes constant...
b) The lorry accelerates uniformly as first but then its acceleration decreases to 0... :| now u tell!

 

[abcde]

I will tell you how i wud have written this:
a) the speed of the lorry increases and then becomes constant...
b) The lorry accelerates uniformly as first but then its acceleration decreases to 0... :| now u tell!

Correct! I would write almost the same:
(a) The speed increases from 0m/s to a maximum of 25 m/s in the first 55s and then remains constant at its maximum value for the rest of the journey.
(b) The acceleration is constant/uniform at first but then decreases to 0 m/s2 at t= 55s/. The acceleration then remains at 0 m/s2 for the rest of the journey.

 

[Usman17]

Hey do we have to mention the time and speed as well? :|

 

[abcde]

not really necessary. Your description is correct. What are you worried about then?

 

[Usman17]

And how come its answer is D :S
38 Which statement is true for all three types of radioactive emission (alpha-particles, beta-particles
and gamma-rays)?
A They are completely absorbed by a thin aluminium sheet.
B They are deflected by electric fields.
C They emit light.
D They ionise gases.
Gamma rays dont ionise or does it :O

 

[Usman17]

Thnx a bundle buddy u r an asset

 

[abcde]

And how come its answer is D :S
38 Which statement is true for all three types of radioactive emission (alpha-particles, beta-particles
and gamma-rays)?
A They are completely absorbed by a thin aluminium sheet.
B They are deflected by electric fields.
C They emit light.
D They ionise gases.
Gamma rays dont ionise or does it :O

Of course they do! All three types of radiation can cause ionization. However the ionizing effect decreases from alpha(most strongly ionizing) to beta (weak ionizing power) to gamma rays(very weak ionizing power).

 

[Usman17]

Ohhhh I forgot Thnx...

 

[Usman17]

Hey dude... The questions in redspots are NOWHERE to be found in the papers on xtreme :S specially the electronics questions... Where have the redspot taken those questions from ? :| Does this mean that these type questions wont be coming :S

 

[abcde]

No, it doesn't mean that. Redspot has questions before 2002 whereas past papers before 2002 are not available on xtreme papers.

 

[Usman17]

No no... The questions in Nov 06 and 07 papers... Even those questions are not on xtreme papers anywhere...!!!