Resource Quiz 4 - schroeder(cs39963 Resource 4 Two...

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schroeder (cs39963) – Resource 4: Two Dimensional Motion - Projectile and Circular Moton – balasubra This print-out should have 29 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 2) 10.0 points A golfer takes two putts to get his ball into the hole once he is on the green. The first putt displaces the ball 4 . 8 m east, and the second 4 . 5 m south. What displacement would have been needed to get the ball into the hole on the first putt? Correct answer: 6 . 57951 m. Explanation: Let : Δ x = 4 . 8 m and Δ y = 4 . 5 m . 4 . 80 m 4 . 50 m R E S θ The east direction and the south direction define legs of a right triangle. The resultant is the hypotenuse, so the displacement is R = radicalBig x ) 2 + (Δ y ) 2 = radicalBig (4 . 8 m) 2 + ( 4 . 5 m) 2 = 6 . 57951 m . 002 (part 2 of 2) 10.0 points What is the direction (in degrees S of E)? Correct answer: 43 . 1524 . Explanation: tan θ = Δ y Δ x θ = tan 1 parenleftbigg Δ y Δ x parenrightbigg = tan 1 parenleftbigg 4 . 5 m 4 . 8 m parenrightbigg = 43 . 1524 , so the direction is 43 . 1524 of S of E. 003 10.0 points Consider the instantaneous velocity of a body. This velocity is always in the direction of 1. the net force at that instant. 2. the least resistance at that instant. 3. the motion at that instant. correct Explanation: Solution: The instantaneous velocity vector will always point in the direction of the motion at that instant. 004 (part 1 of 2) 10.0 points A particle has vectorr (0) = (4 m)ˆ and vectorv (0) = (2 m / s)ˆ ı . If its acceleration is constant and given by vectora = (2 m / s 2 ) (ˆ ı ), at what time t does the particle first cross the x axis? Correct answer: 2 s. Explanation: vectorr ( t ) = vectorr (0) + vectorv (0) t + 1 2 vectora t 2 , so vectorr ( t ) = (4 m) ˆ + (2 m / s) ˆ ı t +( 1 m / s 2 ) (ˆ ı + ˆ ) t 2 = [(2 m / s) t (1 m / s 2 ) t 2 ı +[4 m (1 m / s 2 ) t 2 ] ˆ vectorr ( t ) will not have a y component when 4 m (1 m / s 2 ) t 2 = 0 (1 m / s 2 ) t 2 = 4 m t = 2 s .
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schroeder (cs39963) – Resource 4: Two Dimensional Motion - Projectile and Circular Moton – balasubra 005 (part 2 of 2) 10.0 points At what time t is the particle moving parallel to the y axis; that is, in the ˆ direction? Correct answer: 1 s. Explanation: vectorr ( t ) = vectorr (0) + vectorv (0) t + 1 2 vectora t 2 vectorv ( t ) = dvectorr d t = vectorv (0) + vectora t , so vectorv ( t ) = (2 m / s)ˆ ı (2 m / s 2 ) (ˆ ı + ˆ ) t = [(2 m / s) (2 m / s 2 ) t ı (2 m / s 2 ) t ˆ vectorv ( t ) will not have an x component when 2 m / s (2 m / s 2 ) t = 0 t = 1 s . At this time vectorv ( t ) = (2 m / s)ˆ parallel to the y -axis. 006 (part 1 of 2) 10.0 points A particle at rest undergoes an acceleration of 1 . 5 m / s 2 to the right and 3 . 8 m / s 2 up. a) What is its speed after 6 . 9 s? Correct answer: 28 . 1888 m / s. Explanation: Basic Concepts The direction of the motion depends only on the horizontal and vertical components of the velocity at any moment.
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