# Q4S - [Answer in terms oF m and v .] b. Describe the motion...

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Quiz 4 Solutions Check the best answer. 1. A pair of blocks, with m 2 = 2 m 1 , have a spring between them to which they are not attached. They are pushed together to compress the spring and then released from rest. When they have left the expanded spring: They have the same speed. m 2 has greater kinetic energy than m 1 . They have the same magnitude of momentum. None of the above is true. Check T or F depending on whether the statement is true or false. 2. The total kinetic energy of any system is equal to one-half the total mass times the square of the speed of the CM. T F [Plus K relative to the CM.] m 1 m 2 Physics 53 Summer 2010 1

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3. A freworks rocket is shot vertically into the air. At the top oF its ±ight an explosion takes place, breaking the rocket into pieces oF mass m and 2 m . The lighter piece moves horizontally toward the north immediately aFter the explosion, with speed v 0 . a. How much energy did the internal Forces oF the explosion provide?
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Unformatted text preview: [Answer in terms oF m and v .] b. Describe the motion oF the CM oF the system while the pieces are in the air. [What external Forces are acting?] c. IF the lighter piece lands at distance R north oF the original launch point, where does the heavier one land? [Answer in terms oF R .] a. At the instant oF explosion the system is at rest. By conservation oF momentum the heavier mass has speed v /2 . The total kinetic energy is 1 2 mv 2 + 1 2 (2 m )( v /2) 2 = 3 4 mv 2 . This is the energy suppled by the explosion. b. The only external Force is gravity, so the CM Falls straight down. c. The heavier one lands at distance R /2 to the south. The CM lands at the launch point. [Its not that simple iF they dont land at the same time, because the ground supplies another external Force when they land.] Physics 53 Summer 2010 2...
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## This note was uploaded on 10/19/2011 for the course PHYSICS 53L taught by Professor Mueller during the Spring '07 term at Duke.

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Q4S - [Answer in terms oF m and v .] b. Describe the motion...

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