WAEC GCE Physics Obj And Essay/Theory Expo Answer – Nov/Dec 2017

11b)
electrical line of force- this is the line drawn such that the tangent to it at a given point is in the direction of the force acting on a small positive change at the point

11c)
diagrams
at beaker point
potential different accross Q=p d are p
IiQ=I2——eq1
p d across = p d across R
IiS=I2R——eq2
divide eq 1by2
IiQ/IiS=I2P/I2R
R=SP/Q

11d)
resistivity- this is the resistance of a wire unit length and unit cross-sectional area
i;e P=RA/L

11e)
Given: F = 50Hz
L = 10 mH (10×10^-³H)
Inductive reactance, XL = 2πFL
= 2×3.14×50×10×10^-³
= 3..14 ohms

11f)
If voltmeter reads 12V, over the 500 ohms, then using I = V/R
current in the circuit is I = 12/500
I = 0.024A
Hence over the 200 ohms, V = IR
V = 0.024×200
V = 4.8 VOLTS
Voltmeter will read 4.8 volts

9b)
Renewable: Water, corn stalk
Non-renewable: coal, natural gasgas

9c)
A closed is a physical system so far removed from other systems that it does not interact with them.

9d)
heat required to melt = mc∆ + ml
Not sure of the temperature given, if it is -3°C or -5°C, However, *Using -3°C*
Heat = (0.1×2200×3)+(0.1×2.26×10^6)
= 226660 J

9ei)
Given: 75 heart beats in 1 min
Therefore in 1 hour, we have (75×60) heart beats = 4500 heart beats
Also given: 2J of energy is expended in 1 heart beat
Therefore for 4500 heart beats, energy expended = (4500×2) J = 9000J
9eii)
Energy = mc∆
9000 = (0.25×4200×∆)
9000 = 1050∆
∆ = 9000/1050
Temperature rise = 8.57°C

8bi)
bodies are streamline to make sure that the surface are in head on contact with the fluid during motion
8bii)
i)aircrafts
ii)ship

8ci)
diagrams
8cii)
mass of bucket =1.3kg
speed of loop(v)=7.0ms^-1
radius(s)=1.2m
(x)acceleration (a)
a=rw^2
v=rw
w=v/r
a=r(v/r)^2
a=rv^2/r^2
a=v^2/r
a=(2.0)^2/1.2=49/1.2
a=40.8ms^-2
b)net force (F)
F=F1-Fg
F=Ma-Mg
F=(1.3*40.8)-1.3*19i
F=53-04-13
F=40N

4b)
the magnitude of the initial speed (u) is equal to the magnitude of the height attained