
(a) When do we say that work is done? Write the formula for the work done by a body in moving up against the gravity. Give the meaning of each symbol which occurs in it.
(b) How much work is done when a force of $2\,N$ moves a body through a distance of $10\,cm$ in the direction of force?
Answer
410.7k+ views
Hint:In physics, when a body is applied with some definite magnitude of force it causes the body to displace and it covers some distance, in order to cover this distance body has some form of energy in it this simple amount of energy needed to cause a displacement of body is called work done by the body.
Complete step by step answer:
(a) When a non-zero magnitude of force is applied on the body and it covers a non-zero magnitude of distance with the condition that the direction of force and displacement must not be ${90^ \circ }$ , then it’s said that work is done on a body. Work is a scalar quantity.
Let us suppose the body moves through a distance of height $h$ while moving up against the gravity now the direction of force of gravity is $ - mg$ since it’s in downward direction and the distance is in upward direction so, Force and distance makes an angle of ${180^0}$ .
Work done is calculated as: $W = F.S.\cos (\theta )$
Where, $F$ is the magnitude of force equals to $ - mg$, $S$ Is the distance it covers which is equals to $h$ and $\theta $ Is the angle between force and displacement which is equals to ${180^0}$.
So, $W = - mgh\cos ({180^0})$
$\therefore W = mgh$
Hence, the work done by the body while moving up against gravity is $W = mgh$.
(b) Since, magnitude of force is given that $F = 2N$
Displacement $S = 10\,cm = 0.1\,m$
Since both are in same direction, so $\cos {0^0} = 1$
$W = F.S$
$\Rightarrow W = 2 \times 0.1$
$\therefore W = 0.2\,J$
Hence, the work done by the body is $W = 0.2\,J$.
Note:Remember that, Force is a vector quantity and displacement is also a vector quantity since, we take the dot product of both force and displacement hence, work done on the body is always a scalar quantity and SI unit of work I same as that of energy which is Joules.
Complete step by step answer:
(a) When a non-zero magnitude of force is applied on the body and it covers a non-zero magnitude of distance with the condition that the direction of force and displacement must not be ${90^ \circ }$ , then it’s said that work is done on a body. Work is a scalar quantity.
Let us suppose the body moves through a distance of height $h$ while moving up against the gravity now the direction of force of gravity is $ - mg$ since it’s in downward direction and the distance is in upward direction so, Force and distance makes an angle of ${180^0}$ .
Work done is calculated as: $W = F.S.\cos (\theta )$
Where, $F$ is the magnitude of force equals to $ - mg$, $S$ Is the distance it covers which is equals to $h$ and $\theta $ Is the angle between force and displacement which is equals to ${180^0}$.
So, $W = - mgh\cos ({180^0})$
$\therefore W = mgh$
Hence, the work done by the body while moving up against gravity is $W = mgh$.
(b) Since, magnitude of force is given that $F = 2N$
Displacement $S = 10\,cm = 0.1\,m$
Since both are in same direction, so $\cos {0^0} = 1$
$W = F.S$
$\Rightarrow W = 2 \times 0.1$
$\therefore W = 0.2\,J$
Hence, the work done by the body is $W = 0.2\,J$.
Note:Remember that, Force is a vector quantity and displacement is also a vector quantity since, we take the dot product of both force and displacement hence, work done on the body is always a scalar quantity and SI unit of work I same as that of energy which is Joules.
Recently Updated Pages
Glucose when reduced with HI and red Phosphorus gives class 11 chemistry CBSE

The highest possible oxidation states of Uranium and class 11 chemistry CBSE

Find the value of x if the mode of the following data class 11 maths CBSE

Which of the following can be used in the Friedel Crafts class 11 chemistry CBSE

A sphere of mass 40 kg is attracted by a second sphere class 11 physics CBSE

Statement I Reactivity of aluminium decreases when class 11 chemistry CBSE

Trending doubts
10 examples of friction in our daily life

One Metric ton is equal to kg A 10000 B 1000 C 100 class 11 physics CBSE

Difference Between Prokaryotic Cells and Eukaryotic Cells

State and prove Bernoullis theorem class 11 physics CBSE

What organs are located on the left side of your body class 11 biology CBSE

How many valence electrons does nitrogen have class 11 chemistry CBSE
