Q&A - PSLE Science

[ruyu]

Nebbermind:

MOE Hater:

Ok lets take it ur way:


If the books remain the same it means the height remains the same , the PE remains the same so the KE of the car (converted from PE) will also be the same. Hence the ball's ke will be the same and so should move the same distance.

So this means in this expermiment, the distnace travelled by the ball will be the same irrespective of the angle.

???
Is that what you want to say?

No, coz the ball can only move in the horizontal direction while the car coming down the slope will have horizontal and vertical velocity. Hitting the ball flatly from the top will not cause it to move forward.

jeez finally someone to support me.........

[MOE Hater]

Nebbermind:

the books MUST NOT change as this WILL CHANGE the Potential Energy of the car.


Since this cannot change, the only way to change the angle of the slope is by increasing or decreasing the length of the ramp. Therefore it's A & C.

The greater the angle of inclination of the ramp, the greater the distance travelled by the ball. However, this is not a direct relationship. The greater inclination increases the car's potential energy. This is converted to more kinetic energy when released, and when it hits the ball, the ball would in turn possess greater kinetic energy. This is what enables it to travel a greater distance. So, in conclusion, the potential energy of the car MUST change for the set-up to work.

[Dharma]

Sun_2010:

Hi,


Just wanted to check on this question from 2009 Rosyth SA2 p6


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

The answer given is 1
I think it should be B and C ( there is no such option)

:?:

Hi,

Think that the clue is given in the question \" ... The FORCE of the toy car rolling down ...\".

The force acting on the toy car are gravitational and frictional. Frictional is irrelevant here as the ramp used is the same.

So, the steeper the slope, the greater the gravitational force acting on the toy car.

To make the slope steeper, we should not increase the number of books cause the distance the ball moves will be influenced by the change in energy (GPE to KE) besides the change in the gravitational force in the toy car.

If we do not increase the number of books we must also make sure that the point where the toy car is released is on the ramp just above the highest book.

Agree with the given answer (1)

[Nebbermind]

MOE Hater:

So, in conclusion, the potential energy of the car MUST change for the set-up to work.

the question asked how the slope affect the distance...

if u increase the books, it will change both the height and the slope. so the experiment will not be conclusive.

in any case, if u increase the books, the position of the car will not be the same, ie, higher. Then C is no longer an option.

[Dharma]

MOE Hater:

Nebbermind:

the books MUST NOT change as this WILL CHANGE the Potential Energy of the car.


Since this cannot change, the only way to change the angle of the slope is by increasing or decreasing the length of the ramp. Therefore it's A & C.

Ok lets take it ur way:

If the books remain the same it means the height remains the same , the PE remains the same so the KE of the car (converted from PE) will also be the same. Hence the ball's ke will be the same and so should move the same distance.

So this means in this expermiment, the distnace travelled by the ball will be
the same irrespective of the angle.

???
Is that what you want to say?

If the height of ramp is fixed then change in inclination of the ramp will affect the force acting on the toy car.

When the toy car rolls down, the net force acts downward along the ramp. This downward force is mainly gravity assuming the ramp is frictionless.

When the inclination of the ramp is increased, the vertical component of the net force on the toy car increases. This will cause the ball to move a longer distance when hit by the toy car.

When the inclination of the ramp is decreased, the vertical component of the net force on the toy car decreases. This will cause the ball to move a shorter distance when hit by the toy car.

[Tang]

Dharma:

Sun_2010:

Hi,


Just wanted to check on this question from 2009 Rosyth SA2 p6


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

The answer given is 1
I think it should be B and C ( there is no such option)

:?:

Hi,

Think that the clue is given in the question \" ... The FORCE of the toy car rolling down ...\".

The force acting on the toy car are gravitational and frictional. Frictional is irrelevant here as the ramp used is the same.

So, the steeper the slope, the greater the gravitational force acting on the toy car.

[I thought gravitational force is dependent on the mass of thee toy car and has nothing to do the slope or its height.]

To make the slope steeper, we should not increase the number of books cause the distance the ball moves will be influenced by the change in energy (GPE to KE) besides the change in the gravitational force in the toy car.

If we do not increase the number of books we must also make sure that the point where the toy car is released is on the ramp just above the highest book.

Agree with the given answer (1)

Hello,

See highlight in blue.[/b]

[Tang]

Dharma:

MOE Hater:

[quote=\"Nebbermind\"]the books MUST NOT change as this WILL CHANGE the Potential Energy of the car.


Since this cannot change, the only way to change the angle of the slope is by increasing or decreasing the length of the ramp. Therefore it's A & C.

Ok lets take it ur way:

If the books remain the same it means the height remains the same , the PE remains the same so the KE of the car (converted from PE) will also be the same. Hence the ball's ke will be the same and so should move the same distance.

So this means in this expermiment, the distnace travelled by the ball will be
the same irrespective of the angle.

???
Is that what you want to say?

If the height of ramp is fixed then change in inclination of the ramp will affect the force acting on the toy car.

[Please see my earlier comments. Gravitational force has nothing to do with height or inclination.

When the toy car rolls down, the net force acts downward along the ramp. This downward force is mainly gravity assuming the ramp is frictionless.

When the inclination of the ramp is increased, the vertical component of the net force on the toy car increases. This will cause the ball to move a longer distance when hit by the toy car.

I thought it is the horizontal force that affects how far the ball moves and not the vertical force.

When the inclination of the ramp is decreased, the vertical component of the net force on the toy car decreases. This will cause the ball to move a shorter distance when hit by the toy car.[/quote]
Hello,

Please see highlight in blue.

[Tang]

Nebbermind:

MOE Hater:

So, in conclusion, the potential energy of the car MUST change for the set-up to work.

the question asked how the slope affect the distance...

if u increase the books, it will change both the height and the slope. so the experiment will not be conclusive.

in any case, if u increase the books, the position of the car will not be the same, ie, higher. Then C is no longer an option.

Hello,

Slope refers to the angle of inclination.

Position refers to which part (top end, middle, lower portion, etc.) of the ramp and not its height. If the length of the ramp is changed, the position is no longer the same.

[Nebbermind]

Tang:

Dharma:

[quote=\"MOE Hater\"]
Ok lets take it ur way:

If the books remain the same it means the height remains the same , the PE remains the same so the KE of the car (converted from PE) will also be the same. Hence the ball's ke will be the same and so should move the same distance.

So this means in this expermiment, the distnace travelled by the ball will be
the same irrespective of the angle.

???
Is that what you want to say?

If the height of ramp is fixed then change in inclination of the ramp will affect the force acting on the toy car.

[Please see my earlier comments. Gravitational force has nothing to do with height or inclination.

When the toy car rolls down, the net force acts downward along the ramp. This downward force is mainly gravity assuming the ramp is frictionless.

When the inclination of the ramp is increased, the vertical component of the net force on the toy car increases. This will cause the ball to move a longer distance when hit by the toy car.

When the inclination of the ramp is decreased, the vertical component of the net force on the toy car decreases. This will cause the ball to move a shorter distance when hit by the toy car.

Hello,

Please see highlight in blue.[/quote]the gravitational force can be resolved into 2 components, one pendicular to the slope and another parallel to the slope. when the slope increase, the force parallel to the slope also increase, causing the car to roll/slide down faster in that direction. when the slope becomes vertical, this component will become Fg, and the car free-fall.

[Nebbermind]

Tang:

Hello,


Slope refers to the angle of inclination.

Position refers to which part (top end, middle, lower portion, etc.) of the ramp and not its height. If the length of the ramp is changed, the position is no longer the same.

It's a matter of interpretation. I had assume 'position' is relative to the tabletop while u have chosen it relative to the ramp.

Like I said before, if u vary both the height and the angle in this experiment, how can one determine whther the ball moves more (or less) due to the additional height or angle?