2010 PSLE Discussion

[James Ang]

Way2GO:

I think James is referring to P6 Science.

It's not so difficult to visualize what James is trying to say once you sketch it:
Let me step you thro' it:
First draw a ball.
Then draw the direction of ball's roll inside the ball eg clockwise direction.
Next, where the ball contact a flat surface eg, draw the direction of ball forward motion ie left to right like so ->
Then draw direction of friction like so <-
Now can you visualize that friction is in the same direction as the ball's roll?

question no 5, O levels physics 2004
http://www.freeexampapers.com/FreeExamPapers.com_.php?__lo=TyBMZXZlbC9QaHlzaWNzL0NJRS8yMDA0IE5vdi81MDU0X3cwNF9xcF8xLnBkZg==


http://www.postimage.org/image.php?v=Ts13uAnr

[James Ang]

VitoRelax:

Way2GO:

I could do it but I don't know how to do it in this forum's format. You just draw a ball..indicate its direction of motion with corresponding friction in opposite direction, then you can see what James means.

My comprehension in language is not so good lah. U think you can point me to a website where I can read ?

Btw, this science topic is about Pri or Sec school ?

Thanks

O levels Pure Physics question but starting to appear in P6 top school exam papers (NY2009) and P6 assessment books. What is your answer to this question?
http://www.postimage.org/image.php?v=gxGG1BJ

[Way2GO]

My answer:

Frictional force acts from left to right at contact surface between wheel and road.
Direction of wheel spin is counter clockwise.

[James Ang]

Way2GO:

My answer:

Frictional force acts from left to right at contact surface between wheel and road.
Direction of wheel spin is counter clockwise.

multiple choice question. A B C or D?

[JonC]

Hah, trick question.


Google and you will find.

Answer is D.

Friction is opp of "v" and "a" is opp of "v", so Friction is same direction as "a".

[James Ang]

JonC:

Hah, trick question.


Google and you will find.

Answer is D.

Friction is opp of \"v\" and \"a\" is opp of \"v\", so Friction is same direction as \"a\".

haha, how do you explain \"a\" and \"v\" to P6 kids when they have not even learn enough about speed to understand that \"velocity\" entails both magnitude and direction.

[tutormum]

Frictional forces exist between surfaces of two objects being in contact. Their direction is always parallel to that surface and opposite to the direction of the intended motion of an object. It is important to emphasize the word intended as frictional forces exist even if there is no motion. Frictional force is an opposing force of any moving object. My explanation is very simple, if a force moves towards the right, the frictional force will move towards the left - exactly opposite each other.

[Way2GO]

JonC:

Friction is opp of \"v\" and \"a\" is opp of \"v\", so Friction is same direction as \"a\".

\"v\" and \"a\" in same direction.

[Way2GO]

tutormum:

Frictional force is an opposing force of any moving object. My explanation is very simple, if a force moves towards the right, the frictional force will move towards the left - exactly opposite each other.

JonC:

Answer is D.

Friction is opp of \"v\" and \"a\" is opp of \"v\", so Friction is same direction as \"a\".

Tricky question indeed.
Referring to dig:
Acceleration to left, the traction is to towards right (force B).
Frictional force is in opposite direction to B; so frictional force is rep by D!

[James Ang]

Way2GO:

tutormum:

Frictional force is an opposing force of any moving object. My explanation is very simple, if a force moves towards the right, the frictional force will move towards the left - exactly opposite each other.

JonC:

Answer is D.

Friction is opp of \"v\" and \"a\" is opp of \"v\", so Friction is same direction as \"a\".

Tricky question indeed.
Referring to dig:
Acceleration to left, the traction is to towards right (force B).
Frictional force is in opposite direction to B; so frictional force is rep by D!

The correct answer is D. The explanation is that the wheel is moving forward but it is round so it is rolling and the direction of the rolling wheel's motion is anti-clockwise, so the motion is backwards or to the right. Direction of fricition is opposite to the direction of the motion so the direction of friction is to the left or D.

This is assuming that the wheel is rolling and not skidding of course!