1. Two men, Joel and Jerry, push against a wall. Jerry stops after10min, while J

Question

1. Two men, Joel and Jerry, push against a wall. Jerry stops after10min, while Joel is able to push for 5 min longer. Compare thework they do: a.) Joel does 50% more work than Jerry b.) Jerry does 50% more work than Joel c.) Joel dos 75% more work than Jerry d.) Neither of them do any work 2. A spring driven dart gun propels a 10.0g dart. It is cockedby exerting a force of 20N over a distance of 5cm. With what speedwill the dart leave the gun, assuming the spring has negligiblemass? Can work be done on a system if there is no motion?

a.) yes, if an outside force is provided
b.) yes, since motion is only relative
c.) no, since a system which is not moving has no energy
d.) no, because of the way work is defined
a.) Joel does 50% more work than Jerry b.) Jerry does 50% more work than Joel c.) Joel dos 75% more work than Jerry d.) Neither of them do any work 2. A spring driven dart gun propels a 10.0g dart. It is cockedby exerting a force of 20N over a distance of 5cm. With what speedwill the dart leave the gun, assuming the spring has negligiblemass? Can work be done on a system if there is no motion?

a.) yes, if an outside force is provided
b.) yes, since motion is only relative
c.) no, since a system which is not moving has no energy
d.) no, because of the way work is defined

Explanation / Answer

1) Work is defined as force times distance so unlessjoel and jerry have super powers niether of them didphysical work. so d is the answer. (note: they gettired because there arms do shake slightly so in a sence they aredoing work but this wouldn't count in a textbook problem) 2) The speed of the dart can be found using conservationof energy: Fd=1/2mv2 (20 N)(.05 m)=(1/2)(.01 kg)v2 v=14.14 m/s Work can never be done without motion. Work can bedefined using heat, but even that is the random motion of atoms andparticles. If there is no motion, then there is noenergy. The answer is d. v=14.14 m/s Work can never be done without motion. Work can bedefined using heat, but even that is the random motion of atoms andparticles. If there is no motion, then there is noenergy. The answer is d.

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