A point mass m is placed inside a spherical shell of radius R and mass M at a distance R/2 from the centre of the shell. The gravitational force exerted by the shell on the point mass is?
A.
GMm/R2
B.
GMm/R
C.
Zero
D.
4GMm/R2
Answer: Option C
Explanation:
At the inner position of the shell, the gravitational field intensity (E) is zero. Therefore, F=mE=0.
A man is standing on an international space station which is orbiting earth at an altitude 520km with a constant speed 7.6km/s. If the man’s weight is 50kg, his acceleration is?
A.
7.6 km/s2
B.
7.6 m/s2
C.
8.4 m/s2
D.
10 m/s2
Answer: Option C
Explanation:
gh=R2/(R+h)2 g gh=(6400×103)2/[(6400+520)×103]2 ×10=8.4m/s2.
