### Question 1A

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 **t**2

(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

**R**to at least 1 d. p. in cm

**m**in grams

**t**to at least 1 d.p in seconds and in t

trend: as **m** increases **t** decreases

**t2**to at least 2 d. p.

**a**=

**T**= ( 10 – a)

**m, t, t2, a,T**and in distinguished both axes

**two**of the following precautions

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 = u22gh **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