It weakened the gravitational force between the oblects.
The correct order they go in is "1-4-2-3" The correct answer is D.
Answer:
(a) 
(b) 
Explanation:
For part (a)
As we know that

For part (b)
The power in unit of horsepower is:

Answer:
260 km
65 km/hr
Explanation:
The displacement of an object is the distance moved by that object in a particular direction.
velocity = displacement / time, therefore,
Displacement = velocity * time.
Total displacement for the 4 HR trip = displacement for 2.5 hr + displacement for 1.5 hr
total displacement = (80 * 2.5) + (40 * 1.5)
Total displacement = 200 + 60
Total displacement = 260 Km
average velocity for the total trip = total displacement / total time taken
average velocity = 260 km/ 4 hr
average velocity = 65 km/hr