Question

if a ball is fall on ground from a table , then the work done by gravitational force= mgh.?
when any agent do this it becomes= (-mgh). why it is negative here?please explain

Answer 1

Answer on Question #50657, Physics, Mechanics | Kinematics | Dynamics |

Question

If a ball is fall on ground from a table, then the work done by gravitational force = mgh.? when any agent do this it becomes = (-mgh). why it is negative here? please explain

Answer

The done by gravitational force is equal to the change of potential energy.

Fig.1

If a ball is fall on ground from a table (see Fig.1) the change of potential energy is given by Eq.(1)

$$\Delta E = m g h - 0 = m g h$$

where $m$ is the mass of ball; $h$ is the height of the table; $g = 9.8m / s^2$ gravitational acceleration.

If a ball move from ground to a table the change of potential energy is given by Eq.(2)

$$\Delta E = 0 - m g h = - m g h$$

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