W = Fd = 4(2100) = 8400 J
So the answer is A) 8400 J
I was just rewriting my notes on the work lesson I did in class today, so I saw this question at the perfect time!! :)
Hope it helps!! :)
The gravitational force between two objects is given by:

where
G is the gravitational constant
m1 and m2 are the masses of the two objects
r is the separation between the two objects
The distance of the telescope from the Earth's center is

, the gravitational force is

and the mass of the Earth is

, therefore we can rearrange the previous equation to find m2, the mass of the telescope:
the engine won't start or it sputters when it should be running perfectly. if the gasoline is old and stale, it will have lost a portion of its volatility. the lighter components of the gasoline (remember, gasoline is a mixture of different hydrocarbons) have probably evaporated off or disappeared.
Answer:
They are the only joints that can do 360 degrees and rotate with their own axis. But, because of its free-moving, it is prone to any dislocation compared to other movable joints.
Explanation: