Lesson_4.1_Homework_Solution

Lesson_4.1_Homework_Solution - Lesson 4.1 Homework...

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Lesson 4.1 Homework Solutions 1. Express the following angles in radians. Give your answer as multiples of π . (i) 30 o , (ii) 45 o , (iii) 53 o , (iv) 90 o , (v) 150 o , (vi) 420 o . 5 7 ( ) ( ) ( ) 0.29 ( ) ( ) ( ) 6 4 2 6 3 i ii iii iv v vi π π π π π π 2. What is the angular velocity of the earth (i) in its orbit around the sun, (ii) about its axis? ( i) The earth goes round the sun in 365 days. 7 1 2 , 365 24 60 60 2 365 24 60 60 1.99 10 rad s t s t θ π θ π ω = = × × × = = = × × × × (ii) The earth rotates completely once about its axis in 24 h 5 1 2 , 24 60 60 2 24 60 6 7.3 1 0 0 t s r s t ad θ π θ π ω = = × × = = = × × × 3. A CD-ROM in a computer rotates at 700 rpm. How long will it take for the disc to make one revolution? The time taken for 700 revolutions = 1 minute = 60 s The time taken for one revolution is: 1 60 700 revolutio 0.086 ns s re l s vo = = 4. A turn table set for 45 rpm is turned on and reached its operating speed in 1.25 s. What is the average angular acceleration of the turn table? - 2 1 45 2 0, 45 rpm rad s , 1.25 60 45 2 60 1 . 2 7 5 3 7 . i f f i t s t rad s π ω ω ω ω π α × = = = = × = = = ×
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