Force Flashcards
Define (i)Translational motion (ii)Rotational motion
(i) When a force acts on a stationary, rigid body which is free to move, and displaces it in a straight line in the direction of force is called translational motion
(ii) When a body is pivoted at a point and a force is applied at a suitable point causing it to rotate about the axis passing through the pivoted point is called rotational motion
Factors affecting turning of a body
- The magnitude of force applied
- the perpendicular distance of the line of action of force from the axis of rotation
turning effect of body about axis is due to moment of force applied.
Define moment of force/ Torque
It is the product of the magnitude of force and the prependicular distance of the line of action of the force from the axis of rotation.
Vector quantity
Relationship b/w SI and CGS unit of moment of force
(and kgf/gf)
1 Nm = 105dyne x 102cm
= 107 dyne cm
1 kgf m = 9.8 Nm
1 gf cm = 980 dyne cm
How do you change direction of rotation?
- Change the point of application of force
- Change the direction of force
How to produce maximum turning effect of a body
- Increase magnitude of force
- Apply force at point where the perpendicular distance of the line of action on force from the axis of rotation is maximum
Define static and dynamic equilibrium
- When a body remains in the state of rest despite being under the influence of several forces is static equilibrium
- When a body remains in the same state of motion despite being under the influence of several forces is dynamic equilibrium
What are conditions for equilibrium?
- the resultant of all forces acting on the body should be 0
- The algebraic sum of all moments of forces about the point of rotation should be 0
What is principle of moments?
According to principle of moments, in equilibrium, the sum of anticlockwise moment is equal to the sum of clockwise moment
What is centre of gravity?
Centre of gravity is the point where the algebraic sum of the moment of weights of all the particles constituting the body is 0.
The entire weight of the body can be considered to be acting at this point, however the body is placed
What does the centre of gravity depend on
the position of the centre of gravity depends on the distribution of mass of the body or its shape
Does the centre of gravity of a body have to be within the material of the body? give examples.
It does not always have to be within the material of the body
eg: the centre of gravity of a ring or a hollow sphere lies in its centre where there is no material
What is uniform circular motion?
When a particle moves with a constant speed in a circular path, it is called uniform circular motion
Why is uniform circular motion accelerated motion?
It is because continuous change of direction implies that the velocity is non-uniform i.e accelerated
Difference b/w uniform linear motion and uniform circular motion
- Uniform circular motion has uniform speed but non-uniform velocity which makes it an accelerated motion
- Uniform linear motion has uniform speed as well as uniform velocity which makes it non-accelerated motion
what is centrifugal and centripetal force
- Centrifugal force is the force that acts on a body moving in a circular path, away from the centre of the circular path
- Centripetal force is the force that acts on a body moving in circular motion, in a direction towards the centre of the circular path
Which force is considered fictitious and why?
Centrifugal force is considered fictitious. it is the force assumed by the observer moving in a circular path along with the body.
force of tension of string is the real force
State the centre of gravity of 1. solid/hollow cylinder 2. solid cone 3. hollow cone 4. triangular lamina 5. rectangular/square lamina 6. paralellogram
- midpoint of axis of cylinder
- at height h/4 from the base on the axis
- at height h/3 from the base on the axis
- point of intersection of medians
- points of intersection of diagonals
- points of intersection of diagonals
