Physics 0625/62 February/March 2020: question paper and mark scheme

Question

A student is determining the density of wood by two methods. He is using the wooden rod shown in Fig. 1.1. length wooden rod diameter loop of thread Fig. 1.1 Method 1 The dimensions of the wooden rod are shown full size in Fig. 1.2. l d Fig. 1.2 (a) (i) Measure the length l and the diameter d of the wooden rod in Fig. 1.2. l = …… cm d = …… cm [2] (ii) Suggest an accurate method for measuring the diameter of the wooden rod in this experiment. List any additional apparatus that might be required and briefly describe how you would determine the diameter. You may draw a diagram if it helps to explain your answer. …… [2] (b) The student uses a balance to measure the mass m of the wooden rod as shown in Fig. 1.3. wooden rod 7.8 g Fig. 1.3 Record the mass m of the rod. m = ……g Calculate a value ρ1 for the density of the wooden rod. Use your values from (a)(i) and (b) 4m and the equation ρ1 = . Include a suitable unit. π d2 l ρ1 = …… [2] Method 2 (c) The student pours water into a measuring cylinder as shown in Fig. 1.4. He then floats the wooden rod in the water as shown in Fig. 1.5. 150 160 140 150 Fig. 1.4 Fig. 1.5 Record the reading V1 of the water level in the measuring cylinder as shown in Fig. 1.4. V1 = ……cm3 Record the new reading V2 of the water level in the measuring cylinder with the rod floating in the water as shown in Fig. 1.5. V2 = ……cm3 [1] (d) The student removes the rod and lowers a piece of modelling clay into the water as shown in Fig. 1.6. He then hooks the rod to the modelling clay and lowers them into the water as shown in Fig. 1.7. hook modelling clay Fig. 1.6 Fig. 1.7 He records the new reading V3 of the water level in the measuring cylinder with the modelling clay. He records the reading V4 of the water level in the measuring cylinder with the modelling clay and rod. 164 V3 = ……cm3 178 V4 = ……cm3 Calculate another value ρ2 for the density of the wooden rod. Use the values from (c) and (d) (V2 – V1) and the equation ρ2 = × k where k = 1.0 g / cm3. (V4 – V3) ρ2 = …… [2] (e) Fig. 1.8 On Fig. 1.8, draw an arrow showing the correct line of sight for reading the volume of water in the measuring cylinder. [1] (f) Suggest a possible source of inaccuracy in Method 2, even if it was carried out carefully. …… [1] [Total: 11]

Question

Students are investigating the cooling of hot water in a beaker. They are using the apparatus shown in Fig. 2.1. thermometer 70 beaker 60 50 bench 40 30 20 10 0 Fig. 2.1 (a) Record room temperature θR shown on the thermometer in Fig. 2.1. θR = …… [1] (b) A volume of 150 cm3 of hot water is poured into the beaker and the initial temperature θ is recorded in Table 2.1. The temperature of the water is recorded every 30 s. The values are shown in Table 2.1. (i) Complete the headings in Table 2.1. [1] Table 2.1 t/ θ/ 0 95.0 30 89.0 60 83.5 90 79.0 120 75.0 150 71.5 180 68.5 210 66.0 240 64.0 270 62.5 (ii) Describe one precaution that you would take to ensure that the temperature readings in the experiment are as accurate as possible. …… [1] (c) (i) Calculate the average cooling rate x1 during the first 90 s of the experiment. Use the readings from Table 2.1 and the equation θ0 – θ90 x1 = T where T = 90 s and θ0 and θ90 are the temperatures at t = 0 and t = 90 s. Include the unit for the cooling rate. x1 = …… [1] (ii) Calculate the average cooling rate x2 during the middle 90 s of the experiment. Use the readings from Table 2.1 and the equation θ90 – θ180 x2 = T where T = 90 s and θ90 and θ180 are the temperatures at t = 90 s and t = 180 s. x2 = …… [1] (iii) Calculate the average cooling rate x3 during the last 90 s of the experiment. Use the readings from Table 2.1 and the equation θ180 – θ270 x3 = T where T = 90 s and θ180 and θ270 are the temperatures at t = 180 s and t = 270 s. x3 = …… [1] (d) (i) The temperature of the water falls as time passes. Use the results from (c) to describe the pattern of the rate of cooling of the water during the experiment. Justify your answer by reference to the results. …… [1] (ii) Give an estimate of the probable final temperature θF of the water if left to cool for many hours. θF = …… [1] (e) (i) A student in another school carries out a similar experiment. She starts with the hot water at a lower initial temperature. Suggest how her cooling rates are likely to compare with those calculated in (c). Use the results to explain your answer. suggestion …… explanation …… [2] (ii) State one variable, other than the initial temperature, which the student should control. …… [1] [Total: 11]

Question

A student is investigating a power supply. She is using the circuit shown in Fig. 3.1. power supply P Q crocodile clip l resistance wire Fig. 3.1 (a) The student connects the crocodile clip to a length l = 100.0 cm of the resistance wire and measures the potential difference V0 across terminals P and Q and the current I0 in the circuit. 2 3 0.4 0.6 1 4 0.2 0.8 0 5 0 1.0 V A Fig. 3.2 Fig. 3.3 (i) Record the values of V0 and I0 shown on the meters in Fig. 3.2 and Fig. 3.3. V0 = …… V I0 = …… A [1] (ii) Calculate the resistance R0 of 100.0 cm of the wire. Use your values of V0 and I0 and the V0 equation R0 = . I0 R0 = …… Ω [1] (b) The student then connects the crocodile clip to lengths l = 70.0 cm, 60.0 cm, 50.0 cm, 40.0 cm and 30.0 cm of the resistance wire. She measures the current I in the circuit for each length. Her readings are shown in Table 3.1. Table 3.1 l / cm I /A / 1 1 I A 70.0 0.35 60.0 0.40 2.50 50.0 0.44 2.27 40.0 0.53 1.89 30.0 0.65 1.54 Calculate, and record in Table 3.1, the value of 1 for length l = 70.0 cm of the wire. [1] I / (c) Plot a graph of l / cm (y-axis) against 1 1 (x-axis). You do not need to start your axes at the origin (0,0). I A [4] (d) (i) Determine the gradient G of the graph. Show clearly on the graph how you obtained the necessary information. G = …… [1] (ii) Calculate the electromotive force (e.m.f.) E of the power supply. Use your value of R0 G × R0 from (a)(ii) and the equation E = , where k = 100 cm. k E = ……V [1] (e) The ammeter in this circuit has a small resistance which affects the current. The effect of this resistance on the measured current I will be different for each measured length l of the resistance wire. State and explain which length l will be most affected by the resistance of the ammeter. statement …… explanation …… [2] [Total: 11]

Question

A student investigates a wind turbine, which is an electrical generator driven by a propeller blade. Plan an experiment which will enable him to investigate how the current in a resistor connected across the terminals of the turbine varies with the speed of the air flow through the turbine. The apparatus available includes: a model wind turbine as shown in Fig. 4.1 an electric fan to provide the moving air to turn the turbine a device for measuring air speed. In your plan, you should: • list any additional apparatus needed • complete the wind turbine circuit diagram on Fig. 4.1 • state the key variables to be kept constant • explain briefly how to carry out the experiment, including how the speed of the air flow is to be changed • explain how to use the readings to reach a conclusion. resistor wind turbine propeller blade electric fan bench Fig. 4.1 …… [7] [Total: 7]