Work and Energy

Question 1

Kinetic Energy

Answer 1

• K=1/2 mv²
• Joules

Question 2

Gravitational Potential Energy

Answer 2

• Depends on an object’s position with respect to some level identified as the datum (“ground” or the zero PE position)
• U= mgh
• U= Potential energy
• h= height of the object above the datum

Question 3

Elastic Potential Energy

Answer 3

• Example are springs which are stretched or compressed from the equilibrium length
• U=1/2 kx²
• U= PE
• k= spring constant (Stiffness of the spring)
• x= displacement from equilibrium

Question 4

Total Mechanical Energy

Answer 4

• The sum of an object’s potential and kinetic energies
• E= U+K =0 Conservative Forces (Gravity/Electrostatic forces)
• W_{nonconservative} =Change in E= Change in U+ Change in K (Friction, Air resistance, Fluid Viscosity)

Question 5

Work

Answer 5

• Not energy, but measure of energy transfer
• W=Fd=Fd cos Ø
• Unit= Joule
  *

Question 6

Pressure/ Volume Curve

Answer 6

• Can find the work done on or by a system by finding the area under the pressure-volume curve
• If volume stays constant as pressure changes= no work done (isovolumetric/isochoric process )
• If pressure remains constant as volume changes, the area under the curve is rectangle of length P and width change in velocity (isobaric processes)
• W=PΔV

Question 7

P-V Graph Triangle

Answer 7

• 1/2ΔVΔP

Question 8

P-V Graph Rectangle

Answer 8

• PΔV

Question 9

Power

Answer 9

• Rate at which energy is transferred from one system to another
• P=W/t=ΔE/t
• Unit= Watt (W) (J/s)

Question 10

Work-Energy Theorem

Answer 10

• W_net =ΔK=K_f -K_i

Question 11

Mechanical Advantage

Answer 11

• The ratio of magnitudes of the force exerted on an object by a simple machine (F_out ) to the force actually applied on the simple machine (Fin )
• Mechanical Advantage= F_out / F_in

Question 12

Efficiency

Answer 12

• (Load)(Load distance) / (Effort)(Effort distance)
• Adding more pulleys increases mechanical advantage