Question 5
When a certain star of mass M rotates rapidly, the gravitational force is the centripetal force. The reaction approach zero when the object just remains on its surface.
Question 6
Write 2 PE terms , one for point R and one for point 3R. Find the difference between these 2 PE terms and equate to KE . Hence velocity v can be found.
Question 7
Plot lg (t/yr) vs lg (r/km) . The gradient is n and the intercept is lg A
Question 8
Write g= GM /r2 , but replace M by considering that the planet is has a volume V and density p. The final expression g is directly proportional to r
Question 9
a) Calculate angular velocity by taking GM to be gr2 where g is 9.81 ms-2 and r is 6.38x106 m.
b) Convert angular velocity to period. Show that period is 24 h to be geostationary.
c) The total E = PE + KE
Question 10
Write 2 terms , one for PE at 2Re and one for PE at 3Re. Find the increase in PE . Next find the KE at the 2 locations . Find the decrease in KE. The total change in the addition of change in KE and change in PE.
Question 13
Part c of this question is the same as Question 10
Question 14
The formula for g directly proportional to r as shown in Question 8. hence a straight line from the origin is drawn up to R. Further from R the g is inversely proportional to R2 .
