For each of the following statements, determine whether it is true or false. 1)
ID: 1319464 • Letter: F
Question
For each of the following statements, determine whether it is true or false.
1) Spring A is stiffer than B (kA > kB). Less work must be expended on spring A if both springs are stretched by the same amount.
2) The kinetic energy of an object depends on the direction of the motion involved.
3) The work done to raise a box onto a platform does not depend on how fast it is raised.
4)The friction force is a non-conservative force.
5) The kinetic energy can be negative.
6) The kinetic energy does not depend on the reference frame of the observer.
7)Work can be done in the absence of motion.
8)If the moon revolves around the earth in a perfectly circular orbit, then the earth does do work on the moon.
Explanation / Answer
(1):
false
Work done = (1/2)*k*x^2
greater the k greater will b work done.
(2):
false
KE = (1/2)*m(v.v)
energy is a scalor quantity does not depends on the direction, all it depends on magnitude.
(3):
true
Work done = mgh
all it depends on initial and final state
(4):
very true
friction does depends on te path length , greater the path length greater will be loss in energy hence it is non conservative force.
(5):
no never
KE can never be negative
KE = (1/2)m*v^2
m is always +ve
v ^2 is always positive
therefore KE is always +ve
(6):
true
well, what we know is energy is conserved not KE so KE does depends on frame of reference.
(7):
well, this is a bit tricky question, but as far as system and external forces are concerned then work can never be done until we have motion
so this statement is false.
(8):
never,
centriprittal force applied by earth on moon is always perpendicular to the motion of moon so workdone si zero
so this statement is false.
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