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EDEXCEL Unit 5 Physics Discussions - IAL only

Reply 120

Mouse233

3

Original post by Daniel Atieh

What was the answer for the 2nd mcq about which doesnt affect gravitational force? i selected position. You?

I chose speed of ratation, not so sure...

Reply 121

RoyalBlue7

19

Original post by Daniel Atieh

What did you select for the second mcq? see my post up ..

The answers were

1. Mass of the Earth
2. Mass of the person
3. Rate of rotation of the earth
4. The position of the person.

Weight=GMm/r^2

According to the equation it cannot be (1) or (2).

The question caused some ambiguity by referring to the person at the "surface of the earth". Does that mean that the distance of the centre of mass of the person from the center of the earth is fixed? I think not. "Surface of the earth" is rather vague and may not necessary mean that the position of the person is fixed. So it cannot be (4) as a change in position would not always result in lack of change in the gravitational force he experiences.

I selected (3).

I think its the reaction force that depends on (3). If you use F=ma on the person in the direction of the earth's center where F is the centripetal force then

F = weight - reaction = mrw^2

As the weight is constant it is the reaction force that depends on the rate of rotation.

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(edited 9 years ago)

Reply 122

Ivraj

Original post by saifulahmed

26'C

whoa! i got 20.6 or 21.6....something of that sort

Reply 123

Cemao

It seems that there wasn't any questions on oscillations/SHM... WHY???

Reply 124

janine803

Original post by Ivraj

whoa! i got 20.6 or 21.6....something of that sort

26. it was 26.

and the overall change in KE for all the molecules inside the tennis ball is 0.6J.

Reply 125

BNaeem

Q11) 3 marks for drawing spectrums for 6000K and 5000K (3)

Q12) Felix Baumgartner, 3 marks for calculating the gfs at his height 2 marks for marking GF for earth, 2 marks for why the gfs is constant through the fall (7)

Q13) Saturn, 2 marks for why X has longer wavelength, 3 marks for time period for the ice to orbit Saturn, 3 marks for the mass of Saturn (8)

Q14) Star 4.2 light years away from earth, 2 marks for finding the peak wavelength, 2 marks for finding the luminosity, 3 marks for distance at which the energy flux is equal to that of the sun on the earth (7)

Q15) fission reactor, 2 marks for encasing material and its property, 2 marks for completing the reaction, 2 marks for the speed of the alpha particle, 2 marks for why the Pb nucleus recoils, 2 marks for the speed of the Pb nucleus, 2 marks for why most of the energy goes to the alpha particle, 2 marks for why fusion reactors are being pursued (14)

Q16)pool is heated, 3 marks for how much energy is required to increase the temperature, state one assumption you have made, 2 marks for finding the current flowing through (5)

Q17) tennis ball, 4 marks for explaining why the pressure increases with reduction in volume, 2 marks for finding the temperature, 3 marks for finding the difference in the energies, 2 marks for explaining how the change in the energy effects the bounce (11)

Q18) 2 marks for definition of random and spontaneous, 2 marks for power output being 70 Watts, 3 marks for why this is not suitable for being used as a power source for longer periods (7)

I'm 8 marks short...

Reply 126

samkjr0113

A series of cylindrical steel beams are going to be used to support the roof of one of the buildings being designed. It is known that the volume of the steel being used can increase by a ratio of 1.042:1 during warm weather compared to the volume measured at 250c.

The cylindrical steel beam has a volume of 0.69m3 at 250c and a radius of 0.2m.

If the length of the cylindrical steel beam does not change, calculate the potential increase in the diameter during warm periods.

help please :smile:

Reply 127

DanielDaniels

14

Original post by janine803

26. it was 26.

and the overall change in KE for all the molecules inside the tennis ball is 0.6J.

Right!

Btw, what was the answer for the mcq about resonance? Was it the one related to natural frequency? :/

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Reply 128

DanielDaniels

14

Original post by RoyalBlue7

The answers were

1. Mass of the Earth
2. Mass of the person
3. Rate of rotation of the earth
4. The position of the person.

Weight=GMm/r^2

According to the equation it cannot be (1) or (2).

The question caused some ambiguity by referring to the person at the "surface of the earth". Does that mean that the distance of the centre of mass of the person from the center of the earth is fixed? I think not. "Surface of the earth" is rather vague and may not necessary mean that the position of the person is fixed. So it cannot be (4) as a change in position would not always result in lack of change in the gravitational force he experiences.

I selected (3).

I think its the reaction force that depends on (3). If you use F=ma on the person in the direction of the earth's center where F is the centripetal force then

F = weight - reaction = mrw^2

As the weight is constant it is the reaction force that depends on the rate of rotation.

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Great explanation.
I really dunno what to say, but it's really confusing. Did they actually say which will not affect the gravitational force ON the surface of the earth?

I m still kinda confused :/

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Reply 129

janine803

Original post by Daniel Atieh

Great explanation.
I really dunno what to say, but it's really confusing. Did they actually say which will not affect the gravitational force ON the surface of the earth?

I m still kinda confused :/

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i think the question was "which of the following does NOT affect the gravitational force on a person"....because remember writing out F= GMm/r2 and looking at each variblae...rate of rotation was the only one not in that equation.

Reply 130

RoyalBlue7

19

Original post by Daniel Atieh

Great explanation.
I really dunno what to say, but it's really confusing. Did they actually say which will not affect the gravitational force ON the surface of the earth?

I m still kinda confused :/

Posted from TSR Mobile

On the surface of the earth does not mean the r is constant. The surface of the earth is variable.

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EDEXCEL Unit 5 Physics Discussions - IAL only

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