Physics p1 help needed!

[Talha]

Pls explain da answers of the following questions (physics MCQ's)

(1) explain Ques. 15, 17, 22, 28, 34, http://www.xtremepapers.me/CIE/inde...Level/9702 - Physics/&file=9702_s10_qp_12.pdf

(2) explain Ques. 8, 12, 21, 22, 34 http://www.xtremepapers.me/CIE/inde...Level/9702 - Physics/&file=9702_w10_qp_12.pdf

Urgent help needed... Thnx..

 

[libra94]

Q 15.......efficiency has no units so its D
cuz, mg is kg ms^-2
and F is also kg ms^-2 so when we divide then we get no units

Q 17.....when ice melts, it contracts, so the distance between the atoms decreases and the density (m/v) increases ad the volume decreases
so its B

Q 22.......the frequency for one loop is f
so the frequency for 2 loops will be 2f (u cross multiply)
the answer is C

Q 28........the distance moved by the positive charge is zero
so the work done (force*distance) is therefore zero (A)

Q 34.........let's take the resistance for each resistor as 2ohms
P=I^2R
P is 12 W
R will be [(2*2)/(2+2)]+2 =3 ohms
so find our I which will be 2 A
as resistors Q and R are connected in parallel , they share the current.
the ratio of the currents P : Q: R
is............................2: 1: 1
the current in R is therefore 1 A
power dissipitated is I^2R...so 1^2 * 2ohms= 2W
so the answe is A