can someone explain the chapter easy and fast
gravitation
work and energy
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When force is exerted on an object and object is displaced, work is said to be done.
Work = Force x Displacement
Or, W = F x s
Where, W is work
‘F’ is force and
‘s’ is displacement.
If force, F = 0
Therefore, work done, W = 0 x s = 0
If displacement, s = 0
Therefore, Work done, W = F x 0 = 0
Thus, there are two conditions for work is considered done –
Force should act on the object.
Object must be displaced.
In the absence of any one of the above two conditions, work done will be equal to zero, that is work is not considered as done.
SI unit of work
The SI unit of Force is newton (N) and the SI unit of displacement is meter (m).
Therefore by substituting the SI units of Force and displacement in the expression, W = F x s we get
W = N x m.
Thus, unit force is Nm.
The SI unit of work is joule and is denoted as ‘J’, which is named after an English physicist James Prescott Joule.
The 1 joule of work done is equal to 1N x 1 m.
Or, 1 joule = Nm
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9th science
Work and Energy
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Work
When force is exerted on an object and object is displaced, work is said to be done.
Work = Force x Displacement
Or, W = F x s
Where, W is work
‘F’ is force and
‘s’ is displacement.
If force, F = 0
Therefore, work done, W = 0 x s = 0
If displacement, s = 0
Therefore, Work done, W = F x 0 = 0
Thus, there are two conditions for work is considered done –
Force should act on the object.
Object must be displaced.
In the absence of any one of the above two conditions, work done will be equal to zero, that is work is not considered as done.
SI unit of work
The SI unit of Force is newton (N) and the SI unit of displacement is meter (m).
Therefore by substituting the SI units of Force and displacement in the expression, W = F x s we get
W = N x m.
Thus, unit force is Nm.
The SI unit of work is joule and is denoted as ‘J’, which is named after an English physicist James Prescott Joule.
The 1 joule of work done is equal to 1N x 1 m.
Or, 1 joule = Nm
Direction of Force - Positive and negative work
When force is applied in the direction of displacement, the work done is considered as positive.
i.e. W = F x s
When force is applied in opposite direction of displacement, the work done is considered as negative.
i.e. W = – F x s = – Fs
For example, when engine works to accelerate or move the vehicle, the work done is positive. But when brakes are applied to stop a moving vehicle, i.e. work done against the direction of displacement of the vehicle, the work done is considered as negative.
Energy
Energy is the capacity of doing work.
An object which can do more work is said to have more energy and vice versa. For example, a motorcycle has more energy than a bicycle.
SI unit of energy –
Since energy is capacity of doing work, therefore, the SI unit of energy is same as of work.
Thus, the SI unit of energy is joule and is denoted by ‘J’.
Larger unit of energy is kilo joule and is denoted by kJ.
1kJ = 1000 J
Forms of Energy
There are many forms of energy, such as kinetic energy, potential energy, mechanical energy, chemical energy, electrical energy, etc.
Work = Force x Displacement
Or, W = F x s
Where, W is work
‘F’ is force and
‘s’ is displacement.
If force, F = 0
Therefore, work done, W = 0 x s = 0
If displacement, s = 0
Therefore, Work done, W = F x 0 = 0
Thus, there are two conditions for work is considered done –
Force should act on the object.
Object must be displaced.
In the absence of any one of the above two conditions, work done will be equal to zero, that is work is not considered as done.
SI unit of work
The SI unit of Force is newton (N) and the SI unit of displacement is meter (m).
Therefore by substituting the SI units of Force and displacement in the expression, W = F x s we get
W = N x m.
Thus, unit force is Nm.
The SI unit of work is joule and is denoted as ‘J’, which is named after an English physicist James Prescott Joule.
The 1 joule of work done is equal to 1N x 1 m.
Or, 1 joule = Nm
my_logo
9th science
Work and Energy
PrevNextChapter list
Work
When force is exerted on an object and object is displaced, work is said to be done.
Work = Force x Displacement
Or, W = F x s
Where, W is work
‘F’ is force and
‘s’ is displacement.
If force, F = 0
Therefore, work done, W = 0 x s = 0
If displacement, s = 0
Therefore, Work done, W = F x 0 = 0
Thus, there are two conditions for work is considered done –
Force should act on the object.
Object must be displaced.
In the absence of any one of the above two conditions, work done will be equal to zero, that is work is not considered as done.
SI unit of work
The SI unit of Force is newton (N) and the SI unit of displacement is meter (m).
Therefore by substituting the SI units of Force and displacement in the expression, W = F x s we get
W = N x m.
Thus, unit force is Nm.
The SI unit of work is joule and is denoted as ‘J’, which is named after an English physicist James Prescott Joule.
The 1 joule of work done is equal to 1N x 1 m.
Or, 1 joule = Nm
Direction of Force - Positive and negative work
When force is applied in the direction of displacement, the work done is considered as positive.
i.e. W = F x s
When force is applied in opposite direction of displacement, the work done is considered as negative.
i.e. W = – F x s = – Fs
For example, when engine works to accelerate or move the vehicle, the work done is positive. But when brakes are applied to stop a moving vehicle, i.e. work done against the direction of displacement of the vehicle, the work done is considered as negative.
Energy
Energy is the capacity of doing work.
An object which can do more work is said to have more energy and vice versa. For example, a motorcycle has more energy than a bicycle.
SI unit of energy –
Since energy is capacity of doing work, therefore, the SI unit of energy is same as of work.
Thus, the SI unit of energy is joule and is denoted by ‘J’.
Larger unit of energy is kilo joule and is denoted by kJ.
1kJ = 1000 J
Forms of Energy
There are many forms of energy, such as kinetic energy, potential energy, mechanical energy, chemical energy, electrical energy, etc.
shreshthi:
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Answered by
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the force acting normally on a surface is called thrust.
Pascal:when a force of 1 Newton acts normally on an area of cross s3ction 1 m square then the pressure is one Pascal
the phenomenon due to which a body when immersed in a fluid experience an upward force is known as buoyancy
and Archimedes principal when a body is partially or completed immersed in a fluid , the fluid exerts an upward force on the body which is equal to the weight of the fluid displaced by the body.
Pascal:when a force of 1 Newton acts normally on an area of cross s3ction 1 m square then the pressure is one Pascal
the phenomenon due to which a body when immersed in a fluid experience an upward force is known as buoyancy
and Archimedes principal when a body is partially or completed immersed in a fluid , the fluid exerts an upward force on the body which is equal to the weight of the fluid displaced by the body.
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