Force Flashcards
What is linear motion
When a force acts on a stationary rigid object which is free to move the body starts moving in a straight path in the direction of the force
Eg = a ball moving on the floor
What is rotational motion
Rotational motion can be defined as a motion of an object around a circular path, in a fixed orbit.
Eg = if a wheel is pivoted at its centre and a force is applied the wheel rotates about its center
What is the turning effect of the force
The turning effect on the body about an axis is due to the moment of force applied on the body
What are the Factors affecting turning effect of the body
—> magnitude of force applied
—> perpendicular distance of line of action of force applied on the body
What is torque (moment of force )
Torque is equal to the product of magnitude of the force and the perpendicular distance of line of action of the force from the axis of rotation
Torque = force x perpendicular distance from midpoint
What is SIunit of torque
Nm (Newton meter)
Relation between Nm and dyne cm
1 nm = 10^7 dyne cm
Define couple
–> couple is a pair of forces,
–> 2 equal and opposite parallel forces
–> displaced by perpendicular distance or moment
–> a couple is always needed to produce a rotation
Formula for couple
Moment of couple = either force x perpendicular distance between 2 forces
Define equilibrium of bodies
When a number of forces acting on a body produce no change in its state of rest or of linear or rotational motion, the body is said to be in a state of equilibrium
What are the 2 kinds of equilibrium
—> static equilibrium
—> dynamic equilibrium
Define static equilibrium and give example
When a body remains in a state of rest under the influence of several forces, the body is in static equilibrium
Example = if a book is lying on a table the weight of the book exerted on a table vertically downwards is balanced by an equal and opposite force of reaction exerted by the table on the book vertically upwards
Define dynamic equilibrium and give example
When a body remains in the same state of motion, under the influence of several forces the body is said to be In dynamic equilibrium
Example = an aeroplane moves at a constant height when upward lift on it balances its weight downwards
Conditions for equilibrium
—> the resultant of all forces acting on the body should be zero
—> the algebraic sum of moments of all forces acting on the body about the point of rotation should be zero
What is the principal of moments
If the algebraic sum of moments of all the forces acting on the body, about the axis of rotation is zero, the body is in equilibrium
Sum of clockwise moments = sum of anti clockwise moments
Centre of gravity definition
The centre of gravity of a body is the point about which the algebraic sum of moments of weights of all particles constituting the body is zero.
The entire weight of the body can be considered to act at this point, how so ever the body Is placed
define uniform circular motion
when a particle moves with a constant speed in a ciruclar path, its motion is said to be uniform circular motion
define centripetal force
it is the force acting on a body moving in a circular path, in a direction towards the centre of the circular path
example of centripetal force
–> in an atom the electron revolves around the nucleus in a circular path for which the required centripetal force is obtained form the electrostatic forces of attraction on the negatively charged electron by the positively charged nucleus
define centrifugal force
a force assumed to be acting on the body in a direction away from the centre of circular path is called centrifugal force
example of centrifugal force
–> Mud flying of a tire is one example of the centrifugal force.
what type of force is centrifugal force
it is a fictitious force
the only real force is the force of tension acting towards the centre
