Thread: Theory question on energy

Question:

Select T-True, F-False, for each statement. If the first three statements are T and the rest F, enter TTTFFFFF.

A) The friction force is a conservative force.
B) Work cannot be done in the absence of motion.
C) 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.
D) The kinetic energy can never be negative.
E) If the moon revolves around the earth in a perfectly circular orbit, then the earth does not do any work on the moon.
F) The kinetic energy of an object depends on the direction of the motion involved.
G) The kinetic energy depends on the reference frame of the observer.
H) The work done to raise a box onto a platform does not depend on how fast it is raised.

My computer system does not tell me if an individual one is right or wrong unless I get them all right simulatenously so I'd appreciate it if someone could tell me which one is true and which one is false so that I could isolate my mistake and see what I did wrong.

Any input would be greatly appreciated!
Thanks in advance!

Originally Posted by s3a

Question:

Select T-True, F-False, for each statement. If the first three statements are T and the rest F, enter TTTFFFFF.

A) The friction force is a conservative force.
B) Work cannot be done in the absence of motion.
C) 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.
D) The kinetic energy can never be negative.
E) If the moon revolves around the earth in a perfectly circular orbit, then the earth does not do any work on the moon.
F) The kinetic energy of an object depends on the direction of the motion involved.
G) The kinetic energy depends on the reference frame of the observer.
H) The work done to raise a box onto a platform does not depend on how fast it is raised.

My computer system does not tell me if an individual one is right or wrong unless I get them all right simulatenously so I'd appreciate it if someone could tell me which one is true and which one is false so that I could isolate my mistake and see what I did wrong.

Any input would be greatly appreciated!
Thanks in advance!

Please post your answer string.

CB

Ftfttfff

Originally Posted by s3a

Ftfttfff

G) is T, because in the rest frame of a body it has no KE, while in a frame in relative motion but still inertial, it has non-zero KE.

CB