PHYS 2070 Test 1 Fall 2016 Chapters 1-4

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1 PHYS 2070 Test 1 Fall 2016 Chapters A pepperoni pizza has 2.80 megacalories. Juan eats exactly 1/3 of the pizza. How many kilocalories has he consumed? (One food "calorie" is actually a kilocalorie.) Be sure to use the appropriate number of significant figures. A) 930 kcal B) 933 kcal C) kcal D) kcal E) kcal 2. The period of a pendulum is the time it takes the pendulum to swing back and forth once. If the only dimensional quantities that the period depends on are the acceleration of gravity, g, and the length of the pendulum, L, what combination of g and L must the period be proportional to? Acceleration has dimensions of [L][T-2]. A) g/l B) gl2 C) gl D) gl E) L/ g 3. Approximately 0.1% of the bacteria in an adult human's intestines are Escherichia coli. These bacteria have been observed to move with speeds up to 15 μm/s and maximum accelerations of 166 μm/s2. Suppose an E. coli bacterium in your intestines starts at rest and accelerates at 140 μm/s 2. How much time is required for the bacterium to reach a speed of 10 μm/s? a s b. 14 s c s d s e s f. 11 s 4. When vectors A and B are added together they form vector C and these vectors satisfy the relationship A 2 + B 2 = C 2. Which statement is true for these vectors?

2 A) Vectors A and B must be parallel. B) Vectors A and B must be anti-parallel. C) Vectors A and B must have the same magnitudes. D) Vectors A and B must be perpendicular. E) The magnitude of A is the negative of the magnitude of B. Answer: D 5. If the acceleration vector of an object is directed parallel to the velocity vector, then A) the object is speeding up. B) the object is slowing down. C) the object is moving with a constant velocity. D) the object is turning. E) the object is at rest. Answer: A 6. Vector A has a magnitude of 16.0 m and is pointing eastward. It is rotated clockwise. The component of this vector along west is A) 15.0 m 60% B) 5.47 m. C) 18.7 m. D) 12.4 m. E) 44.0 m. 7. Vector A = 6.0 m and points 30 north of east. Vector B = 4.0 m and points 30 west of north. The resultant vector A + B is given by A) 9.8 m at an angle 64 east of north. 60% B) 9.8 m at an angle 26 north of east. C) 7.2 m at an angle 26 east of north. D) 3.3 m at an angle 26 north of east. E) 3.3 m at an angle 64 east of north. Answer: C Diff: 2 Var: 1 Page Ref: Sec. 3-3

3 8. The motion of a particle is described in the velocity vs. time graph shown. We can say that its speed A) increases. 50% B) decreases. C) increases and then decreases. D) decreases and then increases. E) remains constant. Answer: D 9. Ball A is dropped from rest from a window. At the same instant, ball B is thrown downward; and ball C is thrown upward from the same window. Which statement concerning the balls is necessarily true if air resistance is neglected? A) At some instant after it is thrown, the acceleration of ball C is zero. B) All three balls strike the ground at the same time. C) All three balls have the same velocity at any instant. D) All three balls have the same acceleration at any instant. E) All three balls reach the ground with the same velocity. 10. An object is thrown upwards with a speed of 14 m/s. How high above the projection point does it reach? A) 5.0 m B) 10 m C) 15 m D) 20 m E) 25 m 11. A car is traveling north at 17.7 m/s. After 12 s its velocity is 14.1 m/s in the same direction. Find the magnitude and direction of the car's average acceleration m/s2, South 2.7 m/s2, South

4 0.30 m/s2, North 30% 2.7 m/s2, North 12. A pilot drops a bomb from a plane flying horizontally at a constant speed. Neglecting air resistance, when the bomb hits the ground the horizontal location of the plane will A) be behind the bomb. B) be over the bomb. C) be in front of the bomb. D) depend of the speed of the plane when the bomb was released. E) depend of the mass of the bomb when it was released. Answer: B 13. A basketball is launched with an initial speed of 8.0 m/s, 45 oo above the horizontal. The ball enters the basket 0.96 s after it is launched. What are the distances x and y between the launch point and the basket? A) x = 5.4 m, y = 0.73 m B) x = 7.7 m, y = 0.91 m C) x = 5.4 m, y = 0.91 m D) x = 5.7 m, y = 0.73 m E) x = 5.4 m, y = 5.4 m 30% 14. An archer shoots an arrow horizontally at a target 15 m away. The arrow is aimed directly at the center of the target, but it hits 60 cm lower. What was the initial speed of the arrow? a. 43 m/s 100% b. 125 m/s 60% c. 74 m/s d. 19 m/s

5 15. A jumper in the long-jump goes into the jump with a speed of 12 m/s at an angle of 20 above the horizontal. How far does the jumper jump? A) 3.4 m B) 6.2 m C) 9.4 m D) 15 m E) 18 m Answer: C