Waec Gce 2017 Physics Obj And Theory Answers – Nov/Dec Expo

PHYSICS

 

Question1
(a) Horizontal speed just before it strikes floor = ucos(theta)
= 10cos0°
= 10 m/s

(b) t = √(2g/h)
= √(2*10*1)
= √20
= 4.47s

 

 

Question 4
(a) given: u = 20m/s
t = 4s
g = 10m/s²
h = ?
Using s = ut – ½gt²
s = 20(4) – ½(10)(4)²
s = 0m

(b) The inference is that after 4s, the ball returns back to the plane of projection

 

Question 3
Magnetic materials: ¶ Iron ¶ Cobalt ¶ Nickel

 

Question 2
¶ medical uses
¶ welding and cutting
¶ military uses for defense and counter measures

 

Question 5
The factors that determine the location of a solar power station are
¶ Intensity of sun light
¶ surface slope
¶ feeder capacity of the distribution center

 

 

Question 11
(a) ¶ Electrical method
¶ Contact method

(b) Electric lines of force are imaginary lines drawn in an electric field in such a way that the direction at any point gives the direction of the electric field at such a point

(c) QR = SP

(d) Resistivity is the resistance of a unit length of material of unit cross-sectional area

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

(f) 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

 

 

Question 9
(a) Poor conductors of heat application: ¶ Coat (Trapped air in between the fabric)
¶ The hair and the fur of animals are bad conductors of
heat and they protect them from cold .

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

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

d) heat required to melt = mc∆ + ml
*NB*: 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

e) (i) 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

e) (ii) Energy = mc∆
9000 = (0.25×4200×∆)
9000 = 1050∆
∆ = 9000/1050
Temperature rise = 8.57°C

 

Question 8

a)(i) A force is anything that causes motion
(ii) ¶ contact force
¶ field force

b)(i) Bodies are streamlined so they can overcome to a great extent the viscosity that exists in fluids
(ii) ¶ submarines
¶ seals

8c
i) ¶ Fg is downwards
¶ T1 is upwards

ii) ¶ a = v²/r
a = 7²/1.2
a = 40.8 m/s²

¶ F = ma
= 1.3 × 40.8
= 53N

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