What is the work done by the tension in the string of a simple pendulum?

Define work. How is work measured? When is work done by a force negative?

Define work. Write an expression for work in terms of force and displacement. State the $SI$ unit of work done.

In case of negative work,the angle between the force and displacement is: (in $^o$)

State whether the following statement is true or false:
In order to get minimum work,the angle between force and displacement should be $90^{\circ}$.

Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term 'work'.
$1$. Suma is swimming in a pond.
$2$. $A$ donkey is carrying a load on its back.
$3$. $A$ windmill is lifting water from a well.
$4$. $A$ green plant is carrying out photosynthesis.
$5$. An engine is pulling a train.
$6$. Food grains are getting dried in the sun.
$7$. $A$ sailboat is moving due to wind energy.