Question

when a ball is dropped from a height its speed increases gradually name the force which causes this change in speed

Answer 1

Gravitational force
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Answer 2

This can be explained by Newton’s Law of ‘Universal Gravitation’.

Explanation:

The law states each and every ‘particle in the universe’ attracts every other particle. The attraction happens with a force. The force is directly proptional to the product of the mass. It is also ‘inversely proportional’ to the ‘square of the distance’ between them.  

In another word we can define the law in simple words as every point mass attracts every single other point mass by a force pointing along the line intersecting both points.