Waec physics paper 3 Practice/Sample questions and answers

Waec physics paper 3
Practice/Sample questions and
answers
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[EXPO) = 2017 WAEC QUESTIONS AND
ANSWERS A DAY TO EXAM (CLICK
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You are provided with a retort stand,
boss head, clamp, stop watch slotted
weights, hanger, grooved pulley,
thread, measuring tape and other
necessary materials
(i) Measure and record the radius R of
the pulley.
(ii) Set-up the apparatus as illustrated
in the diagram above, such
that the clamp is 1.5 m above the
floor.
(iii) Tie one end of the thread to the
pulley.
(iv) Tie the other end of the thread to
the hanger.
(v) Slot a mass m = 50 g on the hanger.
(vi) Wind the thread around the
groove of the pulley until the base of
the hanger is at a height h = 1.4 m
above the floor.
Maintain this height h for every other
value of m throughout the experiment.
(vii)Release the mass to unwind the
thread
(viii) Determine and record the time t
taken by the mass m to reach the floor.
(ix) Evaluate t2
(x) Also evaluate a =
, T =
(10 –
) and
=
(xi) Repeat the procedure for four
other values of m = 70 g,90 g,110 g and
130 g.
( xii ) Tabulate your reading
( xiii ) Plot a graph with Cl on the
vertical axis and T on the horizontal
axis.
( xiv ) Determine the slope s , of the
graph
(xv) Evaluate I=
(xvi) State two precautions taken to
obtain accurate results
[ 21 marks]
(b) (i) Define centripetal force
[2 marks]
(ii) An object drops to the ground from
a height of 2.0 m , calculate the speed
with
which it strikes the ground
[ g = 10ms-2 ] [ 2 marks ]
Observation
Part (a) this question was not popular
among the candidates. Candidates are
challenged in
measuring the time of fall of the
weight. Most responding candidates
failed to record the
value of R as demanded in the
question. Few recorded the radius as
6m! Some had problem
in evaluating T =
( 10 – a) However, the graph and slope
were well attempted .
The precautions were well stated.
Part (b) many candidates failed to do
justice to this part. Performance was
poor.
Candidates were expected to
Measure and record Radius of pulley R
to at least 1 d. p. in cm
Record five values of m in grams
Measure and record five values of t to
at least 1 d.p in seconds and in t
trend: as m increases t decreases
Evaluated five values of t2 to at least 2
d. p.
Evaluated five values of a =
Evaluated five values of T =
( 10 – a)
Evaluated five values of
=
Composite table m, t, t2, a,T and
in distinguished both axes
Plot graph using reasonable scales
Draw line of best fit
Evaluate the slope as I =
State any two of the following
precautions
Retort stand / pulley firmly clamped
Avoided parallax error in reading
stop-watch/clock/metre rule/ tape rule
Noted / corrected zero error on stop
watch/ clock/metre rule / tape rule
Repeated readings shown on table.
The expected answers for part (b) are:
b(i) Centripetal force is the inward
force / force acting towards the centre
of the circle
required to keep an object moving with
a constant speed in a circular path
OR
F =
Where the symbols have their usual
meanings
(ii) v2 = u2
2gh OR k.E. = P.E.
v2 =02 + 2 x 10 x 2 ½ mv2 = mgh
= 40 v2 = 2 x 10 x 2
v =
v = 6.32 ms-1
= 6.32 ms-1
You are provided with a triangular
glass prism, four optical pins and
other necessary materials.
( i ) Place the triangular glassprism on
a drawing paper and draw
its outline UMR Remove the prism .
(ii) Measure and record the value of
the angle at U.
( iii ) Draw a normal to the line UM at
N. Also, draw another line
TN to the normal such that P> = 60°.
Fix two pins at P 1 and P2.
(iv) Replace the prism and fix two
other pins at P3 and P4 such that
the pins appear to be in a straight line
with the images of the
pins at P1 and P 2when viewed from
the side UR . Remove the
prism.
(v) Join points P3 and P4 producing
the line to meet TN produced
at Z. Draw the normal X Y.
(vi) Measure and record the angle of
emergence, e and that of
deviation d .
(vii) Repeat the experiment with P> =
55°, 50°,40° and 35° .
(viii) In each case, measure and record
the corresponding values of
e and d .
(ix) Tabulate your readings.
(x) Plot a graph with d on the vertical
axis and e on the horizontal
axis starting both axes from the origin
(0,0). Join your points
with a smooth curve.
(xi) From your graph, obtain the
minimum deviation dm and the
corresponding angle of emergence.
Hence, calculate the
refractive index n of the prism using
the formula:
(xii) State two precautions taken to
obtain accurate results.
Attach your traces to your answer
booklet.
(b) (i) State the conditions necessary
for total internal
reflection of light to occur.
(ii)The critical angle for a transparent
substance is 39°.
Calculate the refractive index of the
substance.
Observation
Part (a). This was a popular question
among the candidates. Majority of the
candidates performed poorly in
carrying out the tracing and measuring
the angles e and d . Some candidates
did not draw xy perpendicular to side
UR of the triangle hence they could not
score for e. Some few candidates
handled the question with high degree
of accuracy. Candidates had difficult
time in drawing a smooth curve to join
the points of the graph. Some had a
straight line instead and this affected
their deductions.
Precautions were well stated.
Part (b) (i) This part was well handled
by most responding candidates while
part (ii) was poorly attempted.
Candidates were expected to:
Draw 5 complete traces (showing at
least incident ray, emergent ray, and
angle of deviation)
Record value of U in degrees as 60o
o
Measure and record five values of
correctly and in trend
Trend: as
decreases , e decreases
Measure and record five values of d
and in trend.
Trend: as
decreases, d decreases and later
increases.
Record composite table
e and d
Distinguish both axes
Plot graph using reasonable scales
Draw a smooth curve
Evaluate the slope
Deduce dm and corresponding em.
State any two of the following
precautions
– Evidence of sharp pencil/neat traces
– Evidence of enough pin spacing
( about 4 cm apart )
– Ensured pins were vertical / erect
– Avoided parallax error when reading
protractor
– Repeated readings shown on table
The expected answers for part (b) are:
(i) – Light must be travelling from a
dense medium to a less dense medium.
– Angle of incidence in the dense
medium must be greater than the
critical
angle .
(ii) n = refractive index
n =
=
=
= 1.59
You have been provided with a
resistance box, a voltmeter, a key, a
battery and other necessary materials.
(i) Connect the circuit as shown in the
diagram above
(ii) With the key K closed, read and
record the voltmeter reading Vo
(iii) Set the resistance R in the
resistance box equal to 1Ω.
(iv) Close the key, read and record the
potential difference V on the
voltmeter.
(v) Evaluate R-1 and V-1
(vi) Repeat the procedure for five other
values of R = 2Ω =, 3Ω, 4Ω, 5Ω and 6Ω.
(vii) Tabulate your readings.
(x) Plot a graph with V-1 on the
vertical axis and R-1 on the horizontal
axis.
(ix) Determine the slope, s , of the
graph and the intercept, e , on the
vertical axis.
(x) Evaluate e-1
(xi) State two precautions taken to
obtain accurate results.
(b) (i) Define potential difference
between two point
(ii) Explain why the emf of a cell is
greater than the p.d across the cell
when it is
supplying current through an external
resistance.
Observation
Part (a) . This question was popular
among the candidates and
performance was satisfactory.
However, some candidates could not
evaluate the reciprocal of R and V to
the required accuracy. Most candidates
did well in plotting the graph,
determining the slope and evaluation
of intercept. Precautions were well
stated. Majority missed the mark for
accuracy
Part (b). Majority of the candidates
were able to define p.d while they
were unable to explain why the emf of
a cell is greater than p.d
Candidates are expected to:
Measure and record Value of Vo to at
least 1 d.p in volts
Read and record six values of V to at
least 1d.p in volts and in trend
Trend:- as R increases, V increases
Evaluate and record six values of
to at least 3 d.p
– Evaluate and record six values of
to at least 3.d.p
– Composite table R, V,
,
– Distinguish both axes
– Plot graph using reasonable scales
– Draw a line of best fit
– Evaluate the slope
– Deduce
from the intercept C
– State any two of the following
precautions.
e.g.
– Ensured clean terminals/tight
connection
– Avoided parallax error in reading
the voltmeter
Key removed when reading is not
being taken
Noted/corrected zero error in reading
the voltmeter
Repeated readings shown on the table
b(i) The p.d (in volts) between two
points is defined as the work done (in
joules) in
moving a charge of one coulomb from
one point to the other.
(ii) Emf (E) is the work done across
external resistance R and internal
resistance r while
p.d (V) is the work done across the
external resistance R, only.
You are provided with two metre rules,
two knife edges, optical
pin, a known mass and other
necessary apparatus.
(i) Affix the optical pin at the 50 cm
mark of one of the
metre rules supplied, with a sellotape /
plasticine.
(ii) Place the rule horizontally on the
knife edges such that
the knife edges are at the 17.5 cm and
82.5 cm marks.
Record the distance D between knife
edges.
(iii) Mount the other metre rule
vertically with the retort
stand and clamp and place it close to
the pin to measure
the depressions of the metre rule when
the weight M is
suspended at its mid-point.
(iv) Read and record the position ho of
the pointer on the
vertically mounted metre rule, with no
weight suspended
on the horizontal metre rule.
(v) Suspend M at the midpoint of the
metre rule.
(vi) Read and record the new position
of the pointer hi’
(vii) Determine the depression of the
metre rule H =
hj- ho
(viii) Evaluate log H and log D.
(ix) Repeat the procedure with the
knife edges set at
20.0cm and 80.0 cm, 22.5 cm and 77.5
cm and 25.0 cm
and 75.0 cm marks. Each time read
and record the
distance D and h1
(x) Evaluate the depressions H in each
case and log H and
1og D .
(xi) Tabulate your readings.
(xii) Plot a graph with log H on the
vertical axis and log D on
the horizontal axis.
Observation
Part (a). This question was popular
among the candidates and
performance was fairly good. Many
candidates obtained good readings
though for some candidates, it was
negative because they disregarded the
instruction. Some did not record log H
and log D to the required 3 d.p. Graph
was simple and well plotted though
some candidates still matched points.
Precautions were well stated. Part (b)
was fairly attempted.
Candidates were expected to:
– Read and record ho to at least 1 d.p
in cm
– Read and record four values of D to
at least 1 d.p in cm
– Read and record four values of h1 to
at least 1 d.p in cm and in trend
Trend:
– as D decreases h1 decreases
– Determined four values of H =| h1 –
ho|
– Evaluate four values of log H to at
least 3 d.p.
– Evaluated four values of log D to at
least 3 d.p.
– List D, h1,H, log H and log D
composite table
– Distinguish both axes
– Plot graph using reasonable scales
– Draw line of best fit.
– Evaluate slope
– State any two of the following
precautions
e.g.
– Avoided parallax error in reading
meter rule
– Avoided draught
Repeated readings shown on table
Ensured firm clamping of vertical
metre rule
Ensured knife edges are rigid / firm
Ensured that mass was not oscillating /
mass was steady
b(i) Moment of a force about a point is
the product of the force and the
perpendicular
distance of its line of action from the
point.
(ii) Using the principle of moments
m(50 – 38) = 60 ( 38 – 16)
12m = 1320
m= 110g
Using the diagram above as a guide:
(i) Trace the outline ABC of the
equilateral triangular glass
prism provided.
(ii) Remove the prism. Draw a line MN
such that it makes
an angle i = 5° with the normal at N on
side
AB of the
outline.
(iii) Fix two pins at P I and P 2 on MN .
Replace the prism
on its outline.
(iv) Looking through the face BC of the
prism, fix one pin
at P3 and another at P4 such that they
are in a straight
line with the images of the pins at PI
and P
2′
(v) Remove the prism and the pins.
Draw a line to join P 4
and P3 . Produce line P4P 3 to meet
the line BC of the
outline at Q and line MN produced at P
.
Observation
Part (a). This question was not popular
among the candidates. Candidates
were challenged in making traces as
requires. They also exhibited poor
knowledge in measuring angles θ,
due to
poor handling of protractor but they
were able to evaluate θ . Some
candidates did not attach their traces
while some had traces without pin
marks indicating that the experiment
was not actually performed. However,
they were able to plot the graph and
determine the slope.
Part (b). This part were not
satisfactorily answered by majority of
the respondent.
Candidates were expected to
– Draw five complete traces showing at
least incident ray, emergent ray,
from face BC , the normal at N and Q
and the intersection of the incident
and emergent rays)
– Measure and record five values of
measured and recorded in degrees and
in trend.
Trend: as i increases, e increases.
– Measure and record five values of θ
to at least 1 d.p in degrees and in
trend.
Trend: as i increases, decreases.
– Evaluated five values of
= i + e
– List i
. in a composite table
– Distinguish both axes
– Plot graph using appropriate scales
– Draw line of best fit
– Evaluate slope and intercept
– State any two of the following
precautions.
Ensured pins were vertical / erect
Sharp pencil/neat traces (seen from
traces)
Reasonable spacing of pins (about 4cm
apart)
Avoided parallax error in reading
protractor
Repeated readings shown on the table
The expected answers for part (b) are:
b(i) Whenever light travels from air to
glass, the ratio of the sine of the angle
of incidence to
the sine of the angle of refraction is
1.5[2]
OR
Velocity of light in air is 1.5 times
greater than the velocity of light in
glass.
OR
n =
= 1.5
(ii) n = refractive index
n =
OR
C = sin-1
)
= sin-1
= 37.3o
Observation
This was another popular question
among the candidates and satisfactory
readings were obtained. The challenges
encountered by the candidates were in
the plotting of the graph and
interpreting it because of the small
values got from the evaluation of the
reciprocal of I. Precautions are well
stated.
Part (b). Most candidates were able to
explain the electromotive force of a
cell but could not explain how a
galvanometer may be adapted to read
as an ammeter satisfactorily.
Candidates were expected to:
Read and record value of Io to at least
1 d.p in Ampere
– Evaluate Value of Io-1 to at least 3
s.f.
– Read and record five values of I to at
least 1 d.p in amperes and in trend.
Trend:
– as R increases, I decreases
– Evaluate five values of
to at least 3 s.f
– List R, I and
in composite table
– Distinguish both axes
– Plot graph using appropriate scales
– Draw line of best fit
– evaluate slope, intercept and k =
– state any two of the following
precautions:
Key opened when readings are not
being taken
Ensured clean / tight connections
Noted/adjusted/corrected zero error of
ammeter
Avoided parallax error on ammeter
Repeated readings shown on the table
The expected answers for part (b) are:
b(i) The electromotive force of a cell is
the work done in driving a unit of
electric charge round a complete
circuit
OR
The electromotive force of a cell is the
terminal potential difference across a
cell when it does not supply electric
current to an external resistor.
OR
The emf of a cell is the total energy per
coulomb of charge obtained from a cell
C diagram
G = Galvanometer , S = Shunt or low
resistor wire