WAEC PHYSICS PAST QUESTIONS AND SOLUTIONS

  Mr. Gbadamosi .K. Idris

1. Which of the following phenomena causes capillarity of liquids in tubes of narrow bore?      (WAEC 2006 Question 23)

A. Viscosity
B. Surface tension
C. Osmosis
D. Brownian motion
Ans= B. Surface tension is the force acting along the surface of a liquid, causing the liquid surface to behave like a stretched elastic skin.

2. Which of the following physical quantities are derived? (WAEC 2006 Question  21)

I. Area
II. Thrust
III. Pressure
IV. Mass
Ans= I, II, III only

3. A block of volume 3 X 105m3 and density 2.5 X 103kgm-3 is suspended from a spring balance  (g= 10m/s2) with 2/3 of its volume immersed in a liquid of density 900kgm3. Determine the reading of the spring balance. (WAEC 2006 Question  19)

A. 0.18N
B. 0.57N
C. 0.75N
D. 0.93N

Solution

ꝭb= density of block (2.5 X 103kgm-3)
ꝭl= density of liquid (900kgm-3)
m1= mass of block (?)
v1= volume of block (3 X 105m3)
m2= mass of block in liquid (?)
v2= volume of block in liquid (2/3 of 3 X 105m3)

 ꝭb= m1/v1, but m1=?                                              
 So m1= ꝭb X v1                    
 m1= 2.5 X 103kgm-3 X 3 X 105
 m1= 7.5 X 108kg
         
 ꝭl= 900kgm-3
 v2= 2/3 of 3 X 105m3
 m2=  ꝭl X v2
 m2= 900 X 2/3 X 3 X 105
 m2= 1.8 X 108kg
m1= m2 + mass read on spring
7.5 X 108kg = 1.8 X 108 + mass read on spring
Mass read on spring= 7.5 X 108 – 1.8 X 108
Mass read on spring= 5.7 x 108kg
Weight of solid on spring= mass X acceleration due to gravity
= 5.7 X 108 X 10
= 5.7 x 109N but 0.57 X 1010N
Reading on spring balance= 0.57N
Ans= 0.57N

4. A solid body will float in a liquid if its ( WAEC 2007 Question 10)

A. Density is less than that of the liquid
B. Mass is equal to that of the liquid
C. Density is greater than that of the liquid
D. Mass is less than that of the liquid

Ans= A (principle of flotation states that an object will float in a {liquid or gas} when the upthrust exerted upon it by the fluid in which it floats equals the weight of the object) relating this to density the higher the density the higher the mass but with less density less mass, since the liquid has higher density the upthrust on the object increases as such there is tendency of the principle of flotation taking effect.

5. Fusion is not usually used for generating electric power because? ( WAEC 2008 Question  4)

A. No energy is released when fusion takes place
B. Very high temperatures are required to initiate fusion reaction
C. The raw materials needed are not easily available
D. Heavy nuclei are involved
Ans= B fusion is the combination of two hydrogen nuclei and this process requires high temperatures of up to 108 – 109 Celsius