10.1 Review #1

Choose the INCORRECT.
Gravitational Field.

 $g=\frac{GM}{r^2}$  

• gravitational field is force of attraction per unit mass experienced by a test mass.

• r is distance between center of masses

• The direction of the force is the same as that of the gravitational field.

• units N•kg

What is Gravitational Potential Energy (E_P)?

• Work done bringing one body m from infinity to a certain distance of a greater mass M.

• Work done separating one body m to infinity from a certain distance of a greater mass M.

• Work done separating one body m from a mass M.

Choose the INCORRECT statement.

Gravitational Potential Energy at large distances from M

 $E_P=-\frac{GMm}{r}$  

•  $E_P=F\times s$  Ep is the work done ...

•  $E_P=\left(-\frac{GMm}{r^2}\right)\times r$  

•  $mg∆h=-\frac{GMm}{r}$  
  

•  $F_g=-\frac{GMm}{r^2}$  

Choose the INCORRECT statement:

If we are far away from mass M but always under its gravitational field,

• r is a large number

• Ep is a large value

• Ep is a small negative value

• Ep is closer to zero

Choose the INCORRECT statement:

 $mg∆h=-\frac{GMm}{r}$  is it always true?

• Only when m is on the surface of the M

• when g is constant at different heights.

• Never when m is far away from M

• when ∆h = r

Choose the INCORRECT statement:

The Gravitational Potential (V_g)

• Work done per unit mass bringing a small point mass m from infinity to location from M.

• $V_g=\frac{W}{m}$

• $V_g=\frac{F_g\times r}{m}$

• Work done per unit mass bringing a mass m from infinity to location from M.

Choose the INCORRECT statement.

The Gravitational Potential (V_g)

Units: J/kg

• $V_g=\frac{W}{m}$

• $V_g=\frac{-\frac{GMm}{r^2}\times r}{m}$

• $V_g=\frac{-\frac{GMm}{r^2}}{m}$

• $V_g=-\frac{Gm}{r}$

Choose the INCORRECT statement.

The Gravitational Potential (V_g)

Units: J/kg

• Ep = m•Vg (at a specific r)

• Every big mass M has a specific Vg.

• Every big Mass M has a Vg depending on the distance from m

• Vg = Ep/m. (at a specific r)

What is the work needed to get a rocket of mass m from the surface of planet M to 10x10⁶m above it?

• W = m (-5x10⁹ – -26x10⁹)

• W = m (-5x10⁹)

• W = m (-26x10⁹)

• W = m (5x10⁹)

What is the net gravitational potential if an object is under the influence of 2 big masses?

• V_{g net} = V_g1 + V_g2

• V_{g net} = V_g1 – V_g2

• V_{g net} = V_g2 – V_g1