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MPH Seconds 1/10 Sec Speed Distance Time London 5 miles s = d t t = d s d = s x t

Compound Measures: Speed/Distance/Time Speed is a compound measure since it is calculated by dividing one measure (distance) by another measure (time). If s = speed, d = distance and t = time then: s = d t t = d s   d = st These formulae should be remembered but they can always be recalled if forgotten by thinking about the speedometer of car driving along a road. Lets say that the speedometer reads 30 mph. 30 mph means: per, means for each so divide. distance time miles hour 30 = As an example consider a car travelling at an average speed of 30 mph for 60 miles: 60 t 30 = The time taken is 2 hours = The distance travelled is 60 miles 60 = 30 x MPH 24583

Compound Measures: Speed/Distance/Time 1. A car travels 126 miles in 3 hours. Find its average speed. = 42 mph s = d t t = d s d = st s = d t Average speed 1

Compound Measures: Speed/Distance/Time 2. A car travels 40 miles in ¾ of an hour. Find its average speed. = 53.3 mph (1 dp) s = d t t = d s d = st s = d t 40 ¾ or s = Average Speed 2

Compound Measures: Speed/Distance/Time 3. A train completes a 520 km journey at an average speed of 160 km/hr. Find the time taken for the journey. s = d t t = d s d = st t = d s = 3.25 hours t = (3 hours 15 minutes) Time 1

Time 2 Compound Measures: Speed/Distance/Time 4. A train completes a 442 km journey at an average speed of 170 km/hr. Find the time taken for the journey in hours and minutes. s = d t t = d s d = st t = d s = 2.6 = t = Remember: 0.6 hours = 6/10 of 60 minutes 2 hrs 36 mins

Compound Measures: Speed/Distance/Time 5. Sally walked for 3 hours at an average speed of 5.25 mph. Find the distance walked in. s = d t t = d s d = st d = 3 x 5.25 = miles Distance 1

Compound Measures: Speed/Distance/Time 6. Sally walked for 2½ hours at an average speed of 2.7 m/sec. Find the distance walked in km. s = d t t = d s d = st d = 2.7 x 2.5 x 60 x 60 = minutes seconds = 24.3 km m Distance 2

Questions 1 Compound Measures: Speed/Distance/Time 1. A train travels 24 miles in 30 minutes find its average speed. 2. An aeroplane completes a flight of 3600 mile at an average speed of 540 miles/hr. Find the time taken for the journey in hours and minutes. t = d/s = 3600/540 = 6.666… = 6 hours 40 minutes. S = 24/0.5 = 48 mph 3. An motor cyclist completes a journey at an average speed of 65 mph in 3½ hours. Find the distance travelled. d = s x t = 65 x 3.5 = miles 4. A runner ran a 400 m race in 1 min 35 sec. Find his average speed in m/sec. S = 400/95 = 4.2 m/sec (1 d.p) Questions 1

Questions 2 5. A train travels 380 miles in 5 hour 15 minutes. Find its average speed. 6. A car completes the a journey of 570 km at an average speed of 75 km/hr. Find the time taken for the journey in hours and minutes. t = d/s = 570/75 = 7.6 = 7 hours 36 minutes. S = 380/5.25 = 72.4 mph 7. A cyclist completes a race at an average speed of 24 mph in 1 hour 15 minutes. Find the distance travelled. d = s x t = 24 x 1.25 = 30 miles 8. A runner ran a 600 m race in 2 min 17 seconds. Find his average speed in m/sec. S = 600/137 = 4.4 m/sec (1 d.p) Compound Measures: Speed/Distance/Time Questions 2

Compound Measures: Speed/Distance/Time Challenge Question 1. Sunlight takes approximately 8.33 minutes to reach Earth from the Sun. Calculate the speed of light in miles per second. (3 sig fig) S = d/t = /(8.33 x 60) = miles per second minutes miles Not to scale Questions 3

Compound Measures: Speed/Distance/Time Challenge Question 2. Moon light takes approximately 1.31 seconds to reach the Earth. Use your previous answer to calculate the distance to the moon. (3 sig fig). d = s x t = x 1.31 = miles seconds Not to scale Questions 4

Compound Measures: Speed/Distance/Time 1. A train travels 24 miles in 30 minutes find its average speed. 2. An aeroplane completes a flight of 3600 mile at an average speed of 540 miles/hr. Find the time taken for the journey in hours and minutes. 3. An motor cyclist completes a journey at an average speed of 65 mph in 3½ hours. Find the distance travelled. 4. A runner ran a 400 m race in 1 min 35 sec. Find his average speed in m/sec. Questions 1 Worksheet Worksheet 1

5. A train travels 380 miles in 5 hour 15 minutes. Find its average speed. 6. A car completes the a journey of 570 km at an average speed of 75 km/hr. Find the time taken for the journey in hours and minutes. 7. A cyclist completes a race at an average speed of 24 mph in 1 hour 15 minutes. Find the distance travelled. 8. A runner ran a 600 m race in 2 min 17 seconds. Find his average speed in m/sec. Compound Measures: Speed/Distance/Time Questions 2 Worksheet Worksheet 2

Compound Measures: Speed/Distance/Time Challenge Question 1. Sunlight takes approximately 8.33 minutes to reach Earth from the Sun. Calculate the speed of light in miles per second. (3 sig fig) 8.33 minutes miles Moon light takes approximately 1.31 seconds to reach the Earth. Use your previous answer to calculate the distance to the moon. (3 sig fig). Challenge Question seconds Worksheet Not to scale Worksheet 3