91影视

The distance between point A and point B, d = 5.0 m

The magnitude of applied force, F = 2.0 N

The magnitude of the friction force, f = 10 N

The increase in kinetic energy,$鈭�K=35\mathrm{J}$

Use the equation of work relating mechanical energy and thermal energy. Mechanical energy is the sum of kinetic and potential energy. Thermal energy is the energy contained within a system that is responsible for its temperature.

Formulae are as follow:

$$\begin{gathered} W=鈭�E_{mec}+鈭�E_{th} \\ 鈭�E_{mec}=鈭�K+鈭�U \\ 鈭�E_{th}=fd \\ W=F.d \end{gathered}$$

where, $鈭�K$is change in kinetic energy,$鈭�U$ is change in potential energy, f, Fare forces,$鈭�E_{mec},鈭�E_{th}$ are mechanical and thermal energies, d is displacement and W is work done.

The equation for work done is,

$$\begin{gathered} W=鈭�E_{mec}+鈭�E_{th} \\ F.d=鈭�K+鈭�U+fd \end{gathered}$$

So,

$$\begin{gathered} F.d=鈭�K+鈭�U+fd \\ =2.0脳5.0-35-10脳5.0 \\ 鈭�U=-75\mathrm{J} \end{gathered}$$

The work done by gravitational energy will be equal to the change in gravitational potential energy. So,

$W_g=鈭�U=-75\mathrm{J}$

Hence,the amount of work done on the block by the gravitational force is$W_g=-75\mathrm{J}$.

Therefore, the work done by gravitation force can be found using the equation of work relating to energy.