AQA A, Module 4, Jan 03

Could someone please explain to me questions 8, 9 and 10, i.e. how the answers in the mark scheme have been reached. Also, in question 12, what does it mean where it refers to 'gravitational potential gradient'?

Reply 1

F1 fanatic

16

rachel123

Could someone please explain to me questions 8, 9 and 10, i.e. how the answers in the mark scheme have been reached. Also, in question 12, what does it mean where it refers to 'gravitational potential gradient'?

you'll probably get more of a response if you actually tell us what the questions are, then anyone from whatever exam board can help you.

Reply 2

rachel123

OP

8.A capacitor of capacitance 10 µF is fully charged through a resistor R to a p.d. of 20V using the circuit
shown. Which one of the following statements is incorrect?
A The p.d. across the capacitor is 20V.
B The p.d. across the resistor is 0V.
C The energy stored by the capacitor is 2 mJ.
D The total energy taken from the battery during the charging process is 2 mJ.

Correct answer: D, i get why A, B and C aren't incorrect, but i dont get why D is incorrect as i thought the battery just transfers all its energy to the capacitor

9 A model car moves in a circular path of radius 0.8 m at an angular speed of pi/2 rad s-1.
What is its displacement from point P, 6 s after passing P?
A zero
B 1.6 m
C 0.4pi m
D 1.6pi m

Correct answer: B, but everytime i do it i get D :s-smilie:

10 A small mass is situated at a point on a line joining two large masses m1 and m2 such that it experiences no resultant gravitational force. If its distance from the mass m1 is r1 and its distance from the mass m2
is r2, what is the value of the ratio r1/r2 ?
A m1^2/m2^2
B m2^2/m1^2
C √m1/m2
D √m2/m1

Correct answer: C ...this one i just don't get at all

Reply 3

F1 fanatic

16

rachel123

8.A capacitor of capacitance 10 µF is fully charged through a resistor R to a p.d. of 20V using the circuit
shown. Which one of the following statements is incorrect?
A The p.d. across the capacitor is 20V.
B The p.d. across the resistor is 0V.
C The energy stored by the capacitor is 2 mJ.
D The total energy taken from the battery during the charging process is 2 mJ.

Correct answer: D, i get why A, B and C aren't incorrect, but i dont get why D is incorrect as i thought the battery just transfers all its energy to the capacitor

9 A model car moves in a circular path of radius 0.8 m at an angular speed of pi/2 rad s-1.
What is its displacement from point P, 6 s after passing P?
A zero
B 1.6 m
C 0.4pi m
D 1.6pi m

Correct answer: B, but everytime i do it i get D :s-smilie:

10 A small mass is situated at a point on a line joining two large masses m1 and m2 such that it experiences no resultant gravitational force. If its distance from the mass m1 is r1 and its distance from the mass m2
is r2, what is the value of the ratio r1/r2 ?
A m1^2/m2^2
B m2^2/m1^2
C √m1/m2
D √m2/m1

Correct answer: C ...this one i just don't get at all

8) D is incorrect because you lose energy in the resistor also.

9) It's B because after 6 seconds it's gone around the circle 1 and a half times, ie it is on the opposite side of the circle to where it started, so it's displacement is 2xradius = 1.6m

10) You need to balance gravitational forces using Newton's law of gravitation.