Lecture 4 - Midterm 1

Mechanical energy is the sum of:

• potential and kinetic energy

• kinetic and thermal energy

• potential and electrical energy

• only potential

potential and kinetic energy

What is the change of potential energy equal to?

• -W

• +W

• -K

• delta K

-W

In a positive charge:

• U(elec) increases and K decreases as the charge moves toward x = 0.

• U(elec) decreases and K increases as the charge moves toward x = 0.

• U(elec) decreases and K decreases as the charge moves toward x = 0.

• U(elec) increases and K decreases as the charge moves toward x = 0.

U(elec) decreases and K increases as the charge moves toward x = 0. (“Downhill”)

For a negative charge:

• U(elec) decreases and K increases as the charge moves toward x = 0.

• U(elec) decreases and K decreases as the charge moves toward x = 0.

• U(elec) increases and K decreases as the charge moves toward x = 0.

• U(elec) increases and K decreases as the charge moves toward x = 0

U(elec) increases and K decreases as the charge moves toward x = 0. (“Uphill”)

What happens to a charged particle in a electric field?

• exchanges potential energy only

• exchanges kinetic and potential energy

• exchanges kinetic energy only

exchanges kinetic and potential energy

What happens in a curve for two like charges that are initially moving toward each other?

• the potential-energy curve shows they will speed up until the distance separating them is r min, the distance of closest approach, where the kinetic energy is -1.

• the potential-energy curve shows they will slow down until the distance separating them is r min, the distance of closest approach, where the kinetic energy is 1.

• the potential-energy curve shows they will slow down until the distance separating them is r min, the distance of closest approach, where the kinetic energy is zero.

• the potential-energy curve shows they will speeds up until the distance separating them is rmin, the distance of closest approach, where the kinetic energy is zero.

the potential-energy curve shows they will slow down until the distance separating them is r min, the distance of closest approach, where the kinetic energy is zero.

For two opposite charges:

• the initially separating particles slow down (lose kinetic energy, gain potential energy), and eventually stop and reverse direction at the distance of maximum separation rmax.

• the initially separating particles speed up (lose kinetic energy, gain potential energy), and eventually stop and reverse direction at the distance of maximum separation rmax.

• the initially separating particles slow down (gain kinetic energy, lose potential energy), and eventually stop and reverse direction at the distance of maximum separation rmax.

• the initially separating particles slow down (lose kinetic energy, gain potential energy), and eventually stop and reverse direction at the distance of maximum separation r min.

the initially separating particles slow down (lose kinetic energy, gain potential energy), and eventually stop and reverse direction at the distance of maximum separation rmax.

Proton Radiation Therapy:

• destroys liver cells by irradiating them with a beam of high-energy protons

• destroys cancer cells by irradiating them with a beam of high-energy electrons

• destroys cancer cells by irradiating them with a beam of high-energy protons

• destroys glial cells by irradiating them with a beam of high-energy protons

destroys cancer cells by irradiating them with a beam of high-energy protons

The conservation of energy equation is:

Kf +Uf = Ki +Ui

In an isolated system, the mechanical energy is:

• zero

• conserved

• increasing

• 1

conserved

If a ball is going up and slowing down kinetic energy is:

• is zero

• converted to potential energy (U)

• increasing

• constant

• converted to potential energy (U)

gravitational potential energy is:

• Ug =mgh

• Ug =mgv

• Ug =agh

• Ug =mh

Ug =mgh

Potential energy of a charge in a uniform electric field is:

• Uelec = vEx

• Uelec = qEx

• Uelec = qEy

• Uelec = QEx

Uelec = qEx

If the particle is projected with greater speed:

• Emech < qEd

• Emech = qEd

• Emech > qEd

• Emech > qEx

Emech > qEd

Turning point:

• Uelec = Emech

• Uelec > Emech

• Uelec < Emech

Uelec = Emech