In this experiment you will investigate the indentation made by a glass ball in the surface of some modelling clay. You have been provided with: • a glass ball • two 100g masses • a small lump of adhesive putty • a metre rule • a set square.

1. (a)(i)Describe briefly how to use the apparatus in Fig. 3.1 to determine the diameter of the glass ball. [Figure 3.1] Draw a labelled diagram of the arranged apparatus to help your explanation.[3]
2. (a)(ii)Measure and record the diameter D of the glass ball. D = .................................................... mm[1]
3. (b)(i)Measure and record the diameter d₁ of the indentation. d₁ = .................................................... mm[1]
4. (b)(ii)The area of a circle can be calculated using the equation: A = πd²/4 where A is the area and d is the diameter of the circle. Calculate the area A₁ of the indentation with diameter d₁. A₁ = .................................................... mm²[1]
5. (c)(i)• Replace the ball on a different part of the modelling clay under the wooden strip. • Lower the strip so that it rests on top of the wooden ball. • Using the loop of string attach the mass hanger and masses near the end of the wooden strip as shown in Fig. 3.3. [Figure 3.3] Measure and record x and y in metres to the nearest mm. x = .................................................... m y = .................................................... m[1]
6. (c)(ii)Calculate the force F₂ exerted on the modelling clay using the equation: F₂ = 3y/x Show your working. F₂ = .................................................... N[1]
7. (c)(iii)Measure and record the diameter d₂ of the indentation produced by the ball in the clay. Using the equation in (b)(ii), calculate the area A₂ of the circle with diameter d₂. d₂ = .................................................... mm A₂ = .................................................... mm²[1]
8. (d)(i)Using your values of F₂, A₁ and A₂ from (c)(ii), (b)(ii) and (c)(iii) calculate two values of k. Record your answers to a suitable number of significant figures. first value of k = .............................................................. second value of k = ..............................................................[2]
9. (d)(ii)Values of k are assumed to be the same within the limits of experimental accuracy if they are within 10% of each other. Explain whether these results show that the student’s claim is correct.[1]
10. (e)Students in another laboratory obtain different values of A₁ and A₂ using the same arrangement of the apparatus. Identify two variables that should be controlled to ensure similar values of A₁ and A₂ when using modelling clay. 1 2[2]

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