Hmwk_01_Solutions

Hmwk_01_Solutions - Physics 221 Fall 2008 Homework #1...

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1 Physics 221 Fall 2008 Homework #1 Solutions Ch. 1 Due Tues, Sept 2, 2008 1.1 A car is moving along a highway with a speed of v = 60.0 miles/hour. (a) How many significant figures are present in the value of the speed? There are 3 significant figures. In the following questions, give the answer with the correct number of significant figures. (b) What is the value of 9.6667 times the speed v ? 9.6667 v = (9.6667)(60.0 mph) = 580 mph . (c) What is the value of 52 miles/hour plus the speed v ? (52 mph) + (60.0 mph) = 112 mph . (d) Write down the speed v in scientific notation. 60.0 mph = 6.00 ± 10 1 mph . (e) What is the speed in units of meters per second (m/s)? (60.0 mph) 0.447 m/s 1 mph = 26.8 m/s 1.2 A car travels east for 10 miles and then north for 20 miles. What are the magnitude and direction of the net displacement of the car? Let the vector A = (10 miles) east and B = 20 miles north, and C = A + B : Then the magnitude C = A 2 + B 2 = (10 mi) 2 + (20 mi) 2 = 22 mi. The angle between C and A is ² = arctan( B / A ) = arctan(20 mi/10 mi) = arctan(2), giving ² = 63˚ north of east. N S A C B E W
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2 1.3 Consider two vectors A and B with nonzero magnitudes A and B , respectively. (a) Are A and B vectors? Why or why not? No. The magnitudes A and B have no directional character associated with them. (b) If the vector C is given by C = A + B , is it possible that C = 0 where C is the magnitude of C ? Is it possible that C > A + B ? Can C = A + B ? Can C < A + B ? Draw pictures of the vectors to explain and justify your answers.
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Hmwk_01_Solutions - Physics 221 Fall 2008 Homework #1...

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