Force
A force is an agency that changes the shape or state of motion/rest or
direction of a body or tries to change it.
Effects of a Force
1. A footballer uses a force to change the direction of a motion of a ball
.
2. A cyclist uses a bigger force to pedal his bicycle and increase its
speed.
3. A baker uses a force on his dough to shape it into a curry puff.
4. A man uses a force to move a sationary lawnmover.
Unit of Force
We know that the force can produce acceleration in the body.
Acc. To Newton’s seccond law force is defined as the ‘product of mass of
the body and the accleration produced in it’.
Force = mass X accerleration
F = Ma
On this basis following are the units of force.
(i)The SI unit of force is newton or N
One newton is defined as the force required producing an acceleration of
1 m s-2 in a body of mass 1 kg. Thus,
1 newton = 1kg x 1 m s-2
Hence the relation between kgf and newton is, 1 kgf = 9.8 N
Similarly one gram force is defined as the gravitational pull on a body of
mass 1g
1 gf = 1g x 980 cm s-2
= 980g x cm s-2
= 980 dyne
Hence the relation between gf and dyne is, 1 gf = 980 dyne.
, Question Time
Fill in the blanks
1. Force = mass x acceleration
2. Dyne is the unit of F in C.G.S system.
3. 1 kgf = 9.8 N
4. 1 N = 105 dyne
Linear or Translational Motion
Fig 1.1 Translational Motion
When a force acts on a stationary rigid body which is free to move, the
body starts moving in a straight path in the direction of the applied force.
This is called linear or translational motion.
For example in fig 1.1
Rotational Motion
If the body is pivoted at a point and the force is applied on the body at a
suitable point, it rotates the body about the axis passing through the
pivoted point. This is the turning effect of the force and the motion of
body is called the rotational motion.
A force is an agency that changes the shape or state of motion/rest or
direction of a body or tries to change it.
Effects of a Force
1. A footballer uses a force to change the direction of a motion of a ball
.
2. A cyclist uses a bigger force to pedal his bicycle and increase its
speed.
3. A baker uses a force on his dough to shape it into a curry puff.
4. A man uses a force to move a sationary lawnmover.
Unit of Force
We know that the force can produce acceleration in the body.
Acc. To Newton’s seccond law force is defined as the ‘product of mass of
the body and the accleration produced in it’.
Force = mass X accerleration
F = Ma
On this basis following are the units of force.
(i)The SI unit of force is newton or N
One newton is defined as the force required producing an acceleration of
1 m s-2 in a body of mass 1 kg. Thus,
1 newton = 1kg x 1 m s-2
Hence the relation between kgf and newton is, 1 kgf = 9.8 N
Similarly one gram force is defined as the gravitational pull on a body of
mass 1g
1 gf = 1g x 980 cm s-2
= 980g x cm s-2
= 980 dyne
Hence the relation between gf and dyne is, 1 gf = 980 dyne.
, Question Time
Fill in the blanks
1. Force = mass x acceleration
2. Dyne is the unit of F in C.G.S system.
3. 1 kgf = 9.8 N
4. 1 N = 105 dyne
Linear or Translational Motion
Fig 1.1 Translational Motion
When a force acts on a stationary rigid body which is free to move, the
body starts moving in a straight path in the direction of the applied force.
This is called linear or translational motion.
For example in fig 1.1
Rotational Motion
If the body is pivoted at a point and the force is applied on the body at a
suitable point, it rotates the body about the axis passing through the
pivoted point. This is the turning effect of the force and the motion of
body is called the rotational motion.
