Question

When
Explain work
work and conditions for when
were done positive zero Negative
work gravity
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Answer 1

Explanation:

If the object goes up (the height increases so Δh is positive) then the work done by gravity is negative and tries to make the object's KE decrease. If the object goes down (the height decreases so Δh is negative), the work done by gravity is positive so it tries to make the object's KE increase.

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Answer 2

Answer:

POSITIVE WORK: The work done on an object is said to be positive work when force and displacement are in same direction.

Example: When an object moves on horizontal surface, force and displacement acts in same direction. So, work done is positive.

NEGATIVE WORK: The work done is said to be negative work when force and displacement are in opposite direction.

Example: When an object is thrown upwards,the force of gravity is in downward direction whereas displacement acts in upward direction.  

ZERO WORK: The work done is said to be zero when force and displacement are perpendicular to each other or when either force or displacement is zero.

Example: When we hold an object and walk, the force acts in downward direction whereas displacement acts in forward direction.