- #1

danago

Gold Member

- 1,122

- 4

http://img258.imageshack.us/img258/237/41820624ks2.jpg [Broken]

Ive solved it and the magnitude of my answer was correct, but the sign was incorrect. Ill show my working using letters rather than actual values.

Since energy is added the the object by the force F which does work on the object, the net change in energy of the object will be Fx. The only energies of the object which are changing throughout the motion are its gavitational potential energy and its kinetic energy, so the following statement must hold true:

[tex]

Fx = \Delta T + \Delta V_g

[/tex]

Where T is the kinetic energy and V

[tex]

Fx = 0.5m\Delta (v^2 ) + mg\Delta h \Rightarrow \Delta h = \frac{{Fx - 0.5m\Delta (v^2 )}}{{mg}}

[/tex]

Substituting all the given values into the solution derived above gives me an answer of ~0.09, but the solutions say it should be -0.09.

Where am i going wrong?

Thanks in advance,

Dan.

Ive solved it and the magnitude of my answer was correct, but the sign was incorrect. Ill show my working using letters rather than actual values.

Since energy is added the the object by the force F which does work on the object, the net change in energy of the object will be Fx. The only energies of the object which are changing throughout the motion are its gavitational potential energy and its kinetic energy, so the following statement must hold true:

[tex]

Fx = \Delta T + \Delta V_g

[/tex]

Where T is the kinetic energy and V

_{g}is the gravitational potential energy.[tex]

Fx = 0.5m\Delta (v^2 ) + mg\Delta h \Rightarrow \Delta h = \frac{{Fx - 0.5m\Delta (v^2 )}}{{mg}}

[/tex]

Substituting all the given values into the solution derived above gives me an answer of ~0.09, but the solutions say it should be -0.09.

Where am i going wrong?

Thanks in advance,

Dan.

Last edited by a moderator: