Physics Paper 3 WASSCE (SC), 2023

Alternative B

 

Question 1B

 

You are provided with two knife edges of equal height, a set of masses, a short piece of string with a loop at each end, a metre rule and a half-metre rule.

Carry out the following instructions using the diagram above as a guide.

  1. Slide the loop of strings onto the metre rule and place it symmetrically on the two knife edges, P and Q, as shown in Fig. 1a.

Do not change the positions of P and Q throughout the experiment.

  1. Measure and record the height, Y, of C above the surface of the bench as shown in Fig.1a.
  2. Use the loop of string to hang a mass, m = 50 g at C. Measure the new height, y, as shown in Fig. 1b.
  3. Evaluate the depression, d = ( Y – y ) of C.
  4. Evaluate log d and log m.
  5. Repeat the procedure for four other masses, m = 100 g, 150 g, 200 g and 250 g.

In each case, measure y and evaluate d = ( Y – y ), log d and log m.

  1. Tabulate the results.
  2. Plot a graph with log d as ordinate and log m as abscissa.
  3. Determine the slope, s, of the graph.
  4. Given a mass, , use the graph to determine the value of y.
  5. State two precautions taken to ensure good results.

(b)        (i)      Define the term elasticity.
(ii)     A piece of wood 1.5 m long has a cross-sectional area of  with one end of the wood fixed to a wall. Calculate the force required to produce a depression of
[Young’s modulus of wood = ]

 

 

Observation

 

WEAKNESSES: Most candidates could not determine the value of  from the graph when mass       
      STRENGTH: Most candidates successfully carried out the given instructions.                                                           
EXPECTED RESPONSE:

 (a)    OBSERVATIONS [09]

  • Value of Y correctly recorded to at least 1 d.p in cm.                                  
  • Five values of m correctly recorded in grams.                                             

(Deduct ½ mark for each wrong or missing value)

  • Five values of y correctly recorded to at least 1 d.p in cm and in trend     

Trend: As m increases, y decreases.
(Deduct 1 mark for each wrong or missing value)

  • Five values of d = (Y- y) correctly evaluated.                                              

 (Deduct ½ mark for each wrong or missing value)

  • Five values of log d correctly evaluated to at least 3 d.p.                           

(Deduct ½ mark for each wrong or missing value)
(vi)        Five values of log m correctly evaluated to at least 3 d.p.                        
(Deduct ½ mark for each wrong or missing value)

  • Composite table showing m, y, d, log d and log m.                                       

         GRAPH [06]
(i)         Both axes correctly distinguished     (Award ½ mark each)                        
(ii)        Reasonable Scales                              (Award ½ mark each)                        
(iii)       Five points correctly plotted                                                                        
(Deduct 1 mark for each wrong or missing point)
(iv)       Line of best fit                                                                                               

         SLOPE [02]
(i)            Large right-angled triangle                                                                            
(ii)           Dlog d correctly determined                                                                         
(iii)          Dlog m correctly determined                                                                        
(iv)           correctly evaluated                                                                             

        DEDUCTION [02]
log 170 = 2.230                                                                                                                                                                
log d corresponding to log 170  correctly shown on graph                                         
d correctly evaluated                                                                                       
correctly evaluated.                                                                                          

        PRECAUTIONS [02]
Award 1 mark each for any two correct precautions stated in acceptable tense.
Eg:

  • Shielded apparatus from wind/ switched off fans/avoided draught.
  • Avoided parallax error in taking readings on metre rule.
  • Avoided/noted zero error on metre rule/half-metre rule
  • Repeated readings shown on table.
  • Ensured the mass did not touch/rest on the table.
  • Suspended mass should be stable before taking readings

(b)  (i)  Elasticity
is the ability of a deformed body to return to its original shape and size when the force causing the deformation is no longer present or removed.                     
(ii)