4,5,and 6 Hint: Apply the Work-Energy Theorem.I 4. (5 pts) A system consists of

Question

4,5,and 6

Hint: Apply the Work-Energy Theorem.I 4. (5 pts) A system consists of a mass hanging from a vertical spring. The effect of air resistance is small enough to be ignored. The initial gravitational potential energy is 400 J, the initial elastic potential energy is 700 J and the initial kinetic energy is 200 J. Five seconds later the gravitational potential energy is 600 J and the elastic potential moment? energy is 100 J. What is the kinetic energy at this 5. (5 pts) The initial kinetic energy of a mass is 800 J and the initial potential energy of the mass is 500 J. If the final kinetic energy is 300 J and the final potential energy is 400 J, how much work is done by friction? (Assume friction is the only non-conservative force that does work on the mass (5 pts) A potential energy is -200 J. Is this possible? Explain . mass initially has total energy of 1600 J. Friction does -2000 J of work. The final (20 pts) A 10 kg mass is moving to the right along a horizontal surface with friction (coefficien 0 3) A 40 N force is applied at 30° below the horizontal, as shown.

Explanation / Answer

4. Applying energy conservation,

initial = final energy

400 + 700 + 200 = 600 + 100 + KE

KE = 600 J

5. initial energy = 800 + 500 = 1300 J  

final energy = 300 +| 400 =700 J  

Work done by friction = 700 - 1300 = - 600 J  

6. final energy = 1600 + (-2000) = - 400 J  

KE can not be negativem

so PE have to be less than or equal to -400 J.

so this is not possible.

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