Work and Energy

Question 1

Force, Work, Energy

Answer 1

• As a box is being pulled, a force is being applied to it to move a certain distance. Work is being done, because energy is being transferred from the cause of the force to the box being moved

Question 2

Work

Answer 2

• W = F_parallelΔx
• W = F(cosθ)Δx

Question 3

Work/Energy Sign Conventions

Answer 3

• If positive work on an object is done by the system, energy of the object increases
• If positive work is done by the object on the system, energy of the object decreases

Question 4

What is Kinetic Energy?

Answer 4

• When work is done on an object, there is a transfer of energy to the object; the energy of motion is referred to as kinetic energy
• ΔKE = 1/2mΔv²
• ΔKE = KE_final - KE_initial = W_total

Question 5

Final Velocity on Inclined Plane

Answer 5

• v_f² = 2gh

Question 6

What is Gravitational Potential Energy

Answer 6

• Gravitational potential energy is the energy lost to kinetic energy
• ΔPE = mg(y_f - y_i)
• Gravitational potential energy of an object depends only on the vertical separation of that object from the ground
• Not dependent of path; state function

Question 7

Conservation of Energy

Answer 7

• Energy cannont be created nor can it be destroyed, only changed into different forms
• The total energy in the universe is constant
• E_{initial system} + W_{done on system} = E_final

Question 8

Power

Answer 8

• Power is the rate of transferring energy
• It is also the rate of doing work
  
  • Involves time
• P = ΔW/Δt
  
  • 1 Watt = 1 joule/second