Graded Exam # 1

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Liberty University *

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250

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Physics

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Jan 9, 2024

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PHY250_TW | Chapter 3: Dynamics Question 1 Correct 6.00 points out of 6.00 Started on Sunday, January 1, 2023, 5:26 PM State Finished Completed on Sunday, January 1, 2023, 6:09 PM Time taken 42 mins 29 secs Grade 150.00 out of 150.00 ( 100 %) Feedback You’re off to a good start. A course grade of 70% is required to request a transcript. You’ve met that for the first exam already, but if you want to reattempt for a higher grade you can retake this assessment. Study hard for each exam, and consider using tutoring anytime you get stuck. Remember that 10 hours of tutoring are provided to you through your StraighterLine membership. A mass of 4 . 3 kg is accelerated to 6 . 0 m /s when a force of magnitude F is applied to it. If the same force is applied to a mass of 0 . 5 kg, what is the acceleration of this mass? Select one: a. 25 . 8 m /s b. 12 . 9 m /s c. 6 m /s d. 51 . 6 m /s 2 2 2 2 2 My Account 0

Question 2 Correct 6.00 points out of 6.00 Question 3 Correct 6.00 points out of 6.00 An airplane has an initial velocity with respect to the ground of 200 mph in an eastward direction. A strong wind begins to blow with a velocity of 80 mph from north to south. What are the x -and y -components of the total velocity of the plane when the wind is taken into account? Let north be the positive y -direction and east be the positive x -direction. Select one: a. v = +200 mph v = +80 mph b. v = +200 mph v = −80 mph c. v = +80 mph v = +200 mph d. v = +215 mph v = −80 mph The position of an object along the x -axis is described by the formula x = 2 t − 4 t . Which of the following are the correct formulas for the velocity and acceleration of the object? Select one: a. v = 2 t − t , a = 2 t − 4 b. v = 6 t − 4, a = 12 t c. v = (1/2)t − 2 t , a = (5/2) t − (2/3) t d. v = 6 t − 4, a = 6 x y x y x y x y 3 2 2 4 2 5 3 My Account 0

Question 4 Correct 6.00 points out of 6.00 Question 5 Correct 6.00 points out of 6.00 Two small carts, with masses m = 17 kg and m = 23 kg, are attached by two ideal ropes to a steel ball of mass m = 100 kg as shown in the diagram. What are the accelerations of the carts and the ball? Select one: a. 7 m /s b. 9 . 4 m /s c. 22 . 5 m /s d. 16 . 4 m /s e. None of the above Which is the standard unit of time in the metric system? Select one: a. minute b. second c. year d. hour 1 2 b 2 2 2 2 My Account 0

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Question 6 Correct 6.00 points out of 6.00 Question 7 Correct 6.00 points out of 6.00 Consider a rectangle with a base of 0 . 567 m and a height of 1 . 606 m. What is its area? Select one: a. 0 . 910 m b. 0 . 911 m c. 0 . 9106020 m d. 0 . 9106 m Which of the following statements concerning friction is incorrect? Select one: a. The force that prevents two surfaces from sliding across one another is called static friction. b. The force of static friction ( f ) between parallel surfaces in contact is given by: f = μ N . c. Sliding or kinetic friction is the force which acts to stop two surfaces from sliding past one another. d. The force of kinetic friction acts opposite to the direction of motion and is expressed by the following equation: f = μ N . 2 2 2 2 s s s k k My Account 0

Question 8 Correct 6.00 points out of 6.00 Question 9 Correct 6.00 points out of 6.00 Which is not true? Select one: a. A scalar product always produces a scalar. b. A vector product always produces a vector. c. Vector products and scalar products both change sign for angles greater than 90°. d. Scalar products are zero for perpendicular vectors while vector products are zero for parallel vectors. A 100 N object sits on a table and is tugged forwards and backwards by forces F = 1000 N and F = 1500 N, as shown. (Note that the vectors are not drawn to scale.) There are no other forces acting on the object. What is the magnitude of the normal force, F ? Select one: a. 1000 N b. 100 N c. 1500 N d. 400 N 1 2 N My Account 0

Question 10 Correct 6.00 points out of 6.00 Question 11 Correct 6.00 points out of 6.00 Question 12 Correct 6.00 points out of 6.00 Which is not an mks unit? Select one: a. meter b. kilogram c. second d. centimeter A toy soldier attached to a parachute with a mass of 1 . 8 g is thrown from a second story balcony. A few seconds later the velocity of the parachute toy is measured-it is falling down at constant speed of 18 m /s. What is the force of air drag on toy soldier’s parachute? Select one: a. 0 . 018 N b. 1 . 8 N c. 18 N d. 180 N Which is not a reason why measurements are important? Select one: a. They allow us to make quantitative statements. b. They allow us to incorporate mathematics into physics. c. They give us an absolute analysis of the world around us. d. They allow us to indirectly compare different physical situations. My Account 0

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Question 13 Correct 6.00 points out of 6.00 Question 14 Correct 6.00 points out of 6.00 Question 15 Correct 6.00 points out of 6.00 If the cross product of a vector of length 5 and a vector of length 3 results in a vector of length 10, what is the angle between them? Select one: a. −42° b. 0° c. 42° d. 90° Which of the following is a correct statement concerning the velocity of a particle in uniform circular motion? Select one: a. The velocity is in the same direction as the angular velocity. b. The velocity is directed radially inward. c. The velocity is in the same direction as the centripetal acceleration. d. The velocity is constantly changing directions. What is the acceleration of a skydiver at terminal velocity whose mass is 80 kg and cross-sectional area is 14 m . The density of the air he is falling through is 0 . 9984 g /m . The drag coe cient has a value of 0 ﬃ . 485. Select one: a. 15 . 2 m /sec b. 56 . 4 m /sec c. 0 m /sec d. 481 m /sec e. None of the above 2 3 2 2 2 2 My Account 0

Question 16 Correct 6.00 points out of 6.00 Question 17 Correct 6.00 points out of 6.00 Consider a particle of mass m in uniform circular motion on which the centripetal force is increased. Which of the following is correct? Select one: a. The motion will remain uniform. b. The tangential speed will decrease. c. The radius of the circular speed will increase. d. The tangential speed will increase and /or the radius will decrease. You are rollerblading along the strand in Venice Beach, CA. You start at Muscle Beach at a speed of 8 km /hr. After skating 2 . 3 km you hit a pebble and a wheel falls off your skate. Luckily you were going slowly when it happened so you don’t fall down. You take off your skates and walk 10 minutes to the rollerblade repair shop on the strand, which is 0 . 8 km away. Assuming the strand is perfectly straight, what is your average velocity? Select one: a. 0 . 29 km /hr b. 6 . 4 km /hr c. 6 . 7 km /hr d. 4 . 8 km /hr My Account 0

Question 18 Correct 6.00 points out of 6.00 Question 19 Correct 6.00 points out of 6.00 On a merry-go-round, a child undergoes uniform circular motion. Which of the following is the direction of the child’s acceleration vector? Select one: a. the direction of the velocity b. tangent to the perimeter of the merry-go-round c. outward, away from the center of the merry-go-round d. inward, toward the center of the merry-go-round A mass of 5 . 2 kg is accelerated to 4 . 0 m /s when a force of magnitude F is applied to it. If the same force is applied to another object causes it have an acceleration of 1 . 8 m /s , what is the mass of this object? Select one: a. 2 . 3 kg b. 1 . 4 kg c. 12 kg d. 5 . 1 kg e. None of the above 2 2 My Account 0

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Question 20 Correct 6.00 points out of 6.00 Question 21 Correct 6.00 points out of 6.00 Question 22 Correct 6.00 points out of 6.00 Given the position vector , which of the following is the acceleration vector? Select one: a. b. c. d. How can you calculate the magnitude of a vector using scalar products? Select one: a. Multiply it by a unit vector. b. Multiply it by itself and take the square root. c. Multiply it by a known vector. d. Multiply it by a scalar number. Which of the following is not an example of a vector? Select one: a. displacement b. velocity c. acceleration d. mass ( t ) = 4 + 3 t r → t 2 i ^ j ^ ( t ) = 8 t + 3 a → i ^ j ^ ( t ) = 8 a → i ^ ( t ) = + a → 4 3 t 3 i ^ 3 2 t 2 j ^ ( t ) = 3 a → j ^ My Account 0

Question 23 Correct 6.00 points out of 6.00 Question 24 Correct 6.00 points out of 6.00 A ceiling fan has four blades. The distance between the center of the fan and the tip of the blade is 0 . 75 m. The fan is spinning at 300 rev /min. What is the radial acceleration of the blade tip as a multiple of g ? Select one: a. 3 . 2 g b. 740 g c. 23 . 6 g d. 75 . 5 g An electron enters a particle accelerator at a speed of m/s. After the electron exits the accelerator, which is a narrow tube that is 2.0m long. Assuming that the acceleration of the particle is constant , what is the speed of the particle when it exits the accelerator? Select one: a. 9 . 6 × 10 m /s b. 1 . 2 × 10 m /s c. 6 . 2 × 10 m /s d. 5 . 0 × 10 m /s 1.2 × 10 4 0.80 μs −3 4 12 6 My Account 0

Question 25 Correct 6.00 points out of 6.00 Which of the following pairs of vectors have the same direction? Select one: a. b. c. d. Quiz navigation Show one page at a time Finish review = 3 + 2 = 6 + 4 A → i ^ j ^ B → i ^ j ^ = 4 − 2 = −4 − 2 A → i ^ j ^ B → i ^ j ^ = 10 + 8 = 5 + 8 A → i ^ j ^ B → i ^ j ^ = 2 − 2 = 4 + 4 A → i ^ j ^ B → i ^ j ^ 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Sign-up For StraighterLine Updates ABOUT US CAREERS PARTNERS PRESS BLOG Questions? Call Toll Free (877) 787-8375 or Chat with an Enrollment Counselor Email Get Updates My Account 0

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Graded Exam # 1

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