Mr. Study's 3 and 4 Question.

[yawho]

When you in the train looking at the globe, are Newton's first and second laws applicable?

[rife168]

When you in the train looking at the globe, are Newton's first and second laws applicable?

They would not be applicable if one was to not consider the acceleration of the train. Since in this question we know and use the acceleration of the train, they are applicable.
It makes sense intuitively.. If you did not consider the acceleration of the train, then there would be some strange, unexplained force accelerating all objects to one direction.
If the train was traveling at a constant velocity, then it would be an inertial frame of reference, and thus Newton's Laws would hold.
This notion is one of the fundamentals of relativity, I believe.

[yawho]

When you in the train looking at the globe, are Newton's first and second laws applicable?

They would not be applicable if one was to not consider the acceleration of the train. Since in this question we know and use the acceleration of the train, they are applicable.
It makes sense intuitively.. If you did not consider the acceleration of the train, then there would be some strange, unexplained force accelerating all objects to one direction.
If the train was traveling at a constant velocity, then it would be an inertial frame of reference, and thus Newton's Laws would hold.
This notion is one of the fundamentals of relativity, I believe.

When you are in the train looking at the globe, are Newton's first and second laws applicable? yes/no

[rife168]

When you in the train looking at the globe, are Newton's first and second laws applicable?

They would not be applicable if one was to not consider the acceleration of the train. Since in this question we know and use the acceleration of the train, they are applicable.
It makes sense intuitively.. If you did not consider the acceleration of the train, then there would be some strange, unexplained force accelerating all objects to one direction.
If the train was traveling at a constant velocity, then it would be an inertial frame of reference, and thus Newton's Laws would hold.
This notion is one of the fundamentals of relativity, I believe.

When you are in the train looking at the globe, are Newton's first and second laws applicable? yes/no

Not if you don't take into account the fact that your frame of reference is accelerating. I thought I just explained that?

[Mr. Study]

Vertical Motion Question (Woo!)

A hockey ball (puck? hehe) is hit towards the goal at an angle of 25^o to the ground with an initial speed of 32 km h^-1

Part b) How long does the ball spend in flight?

I would like a hint on what I should be doing, I am not too sure what I should be doing.

[Phy124]

For part b) work out the vertical component of the initial velocity then rearrange a formula such as to t = , where v = 0, to calculate the time it will take to get to maximum height and then double that for the entire flight.

[Mr. Study]

Ah! Very smart idea!

EDIT: Ahhh, I get why v is 0. Ha! Thanks so much!!

[Mr. Study]

Ugh, Just when I thought I was getting better at Physics.

From Heinemann. A ball of mass 10g, is falling at a constant speed of 8.2 ms-1. Find the magnitude and direction of air resistance.

Thanks.

[Phy124]

Ugh, Just when I thought I was getting better at Physics.

From Heinemann. A ball of mass 10g, is falling at a constant speed of 8.2 ms-1. Find the magnitude and direction of air resistance.

Thanks.

Constant speed = no acceleration, therefore F_net = 0

Therefore, forces down = forces up

Let F_g = weight force and F_a = force due to air resistance

[Mr. Study]

Hey, Thanks for that.

Sorry for asking it though, it now seems like such a simple question.

[Phy124]

That's no worries at all, I have no problems with answering questions such as this

If you don't ask now, you might come up against it in an Exam and lose easy marks.

[Mr. Study]

Could anyone explain to me what Impulse actually is?

The book tells me that the net impulse = change in momentum but that doesn't really explain what Impulse does/do.

Thank you.

[yawho]

Could anyone explain to me what Impulse actually is?

The book tells me that the net impulse = change in momentum but that doesn't really explain what Impulse does/do.

Thank you.

I think I know this one.
When you exert a force on an object for a period of time, you give the object an impulse in the direction of the force, and the magnitude of the impulse is given by force x time period. If this force is the net force on the object, it causes a change in momentum of the object, which is equal to the impulse of the net force.
Open for discussion.

[Mr. Study]

If we were given the mass and speed of a car and it were travelling over a hill. How would we work at the maximum speed for the car, at the top of the hill, while the wheels are still able to be in contact with the hill?

I have a feeling that the Weight force must be higher than the Normal force but I am not too sure how to do the calculations showing the maximum speed before it will lose contact.

Thanks.

[Phy124]

IIRC, it should go something like this:

Firstly you use the following formula;



Which is:



It will lost contact when , so: