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Quiz4a - a The lighter block A compresses the spring more b...

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Physics 53 Quiz #4a Fall 2007 Name ___________________________ Recit. Section _______ Circle the correct answer: 1. [2 points] A projectile of mass m is launched into the air. When it reaches its greatest height, its speed is only 49.0% of the speed it had when it was released. What fraction of its initial kinetic energy does it retain at the apex of its trajectory? [Neglect air resistance.] a) 24.0%. b) 49.0%. c) 70.0%. d) Its kinetic energy is zero. 2. [3 points] . In the absence of friction if the same relaxed spring is hit by (A) a block of mass m and speed v or (B) a block with mass 4 m and speed v /2, it is compressed by the same amount before they come to a stop. How does the situation change when both blocks have the same kinetic friction coefficient, but still hit the spring with speed v and v /2, respectively?
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Unformatted text preview: a) The lighter block A compresses the spring more. b) The heavier block B compresses the spring more. c) Both still compress the spring by the same amount. 3. [2 points] Two identical bullets are fired into a sandbag, one with twice the speed of the other. If the friction force on the bullets is the same, how much farther will the faster bullet penetrate, if they are stopped within the sandbag? a) 2 times as far. b) Twice as far. c) Four times as far. d) Half as far. 4. [3 points] A (undoped) Tour de France cyclist rides uphill on a 3° incline at a speed of 8.00 m/s. If the rider and the bicycle, together, have a mass of 80.0 kg, and you can neglect friction and air resistance, what is the power output of the athlete? [Use g = 10.0 m/s 2 .] a. 215 W. b. 335 W. c. 558 W. d. 675 W....
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