74 Look at the instruments in the photos and explain what each one could be used for. a) Research which units of measurement each one uses. b) How precise is each instrument? How do you know? c) Write the amounts shown in the photos in another unit. 75 On this graph paper, each square is 1 mm2. Measure the surface area of the boat. 76 In the technology lab, we have a coil of copper wire with a diameter of 1 mm. To find its length, we cut 50 cm of wire and weigh it. The result is 3.5 g. Then we weigh the whole coil. The result is 68 g. Therefore, how many metres of copper wire does the coil have? Converting units 77 Calculate how many seconds there are in a day. 78 Calculate how many days you have lived up to now. Write the amount in seconds. 79 The stopwatch in the photo shows the duration of a video. Explain which of these statements is correct. a) It lasted over 1 000 s. b) It lasted 1 653 s. c) It lasted exactly 16 min. d) It lasted under 16 min. 80 What would the stopwatch show for a film lasting 52.5 minutes? S O LV E D P R O B L E M 8 One way to calculate the rate at which water flows from a fountain is to measure the litres of water it emits per minute. Water flows from the fountain at a rate of 15 L/min. Write it in m3/h. 1. Find the equivalent of each unit you want to convert. 1 m3 = 1 000 L 1 h = 60 min 2. Write the amount you want to convert followed by the conversion factor for the first unit. 15 L min × 1 m 1 000 L 3 3. Then write the conversion factor for the second unit. 15 L min × 1 m 1 000 L 3 × 60 min 1 h 4. Simplify the units. Calculate and write the final result. 15 60 3 ⋅ = 1 000 m h 0.9 m h 3 1st factor 2nd factor 81 Water flows from a fountain at a rate of 15 L/min. Write it in cm3/s. S O LV E D P R O B L E M 9 The speed limit on a US motorway is 85 miles per hour. Write it in m/s. Data: 1 mile = 1.609 km. 1. Find the equivalent of each unit you want to convert. 1 mile = 1.609 km = 1 609 m 1 h = 60 × 60 = 3 600 s 2. Write the amount followed by the conversion factor for the first unit. 85 mile h × 1 609 m 1 mile 3. Then write the conversion factor for the second unit. 85 mile h × 1 609 m 1 mile × 1 3 600 h s 4. Simplify, calculate and write the final result. 85 1 069 3 600 ⋅ = m s 38 m s 1st factor 2nd factor 82 The speed limit on a motorway is 120 km/h. Write it in m/s and in miles per hour. Data: 1 mile = 1 609 m. c h e c k yo u r p r o g r e s s 30
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