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Unformatted text preview: the right, as shown. u
What frictiona l force acts on the wheel where it touches the ground (se e arrow)? a.
d. Answer (a) See Fig. 2.2.6 (a) and its discussion in the book. static frictional force, to the left static frictional force, to the right sliding frictional force, to the left sliding frictional force, to the right PHYS115 – Spring 2013 3 Test 2 - 19 April 2013 Question 6 – You put water in a kitchen blender. After a whil e, it travels in a 12‐cm radius circle at a constant speed of 3 m/s. How hard must the sides of the blen der push inward on 0.006 kg of the spinning water? a. 0.018 N b. 0.027 N c. 0.0065 N d. 0.45 N Answer (d) centripetal force = mass speed2 0.006 32 0.45 N radius
0.12 Question 7 – The baseball’s coefficient of restitution is 0.40. How fast is the baseball after the bat hit it? a.
d. 140 km/h 200 km/h 220 km/h 250 km/h 60 km/h 140 km/h speed = ? 140 km/h Answer (c) see book Fig. 3.2.5 and its discussion Summarizing: Collision speed is 140 + 60 = 200 km/h Rebound speed is (coefficient of restitution) x (collision speed) = 0.40 x 200 = 80 km/h Add speed of bat again: speed becomes 80 + 140 = 220 km/h PHYS115 – Spring 2013 4 Test 2 - 19 April 2013 Question 8 – The driver is pressing on the gas. (a)...
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