CHAPTER 12. FORCE,MOMENTUM AND IMPULSE 12.6
Equilibrium Objects at rest or moving with constant velocity are in equilibrium and have a zero resul-
tant force.
Equilibrant The equilibrant of any number of forcesis the single force required to produce equilibrium.
Triangle Law for Forcesin Equilibrium Three forces in equilibrium can be representedin magnitude
and direction by the three sides of a triangle taken in order.
Momentum The momentum of an object is definedas its mass multiplied byits velocity.
Momentum of a System The total momentum of a system is the sum of the momenta of each of the
objects in the system.
Principle of Conservation of Linear Momentum: ‘The total linear momentum of an isolated system is
constant’ or ‘In an isolated system the total momentum before a collision(or explosion) is equal
to the total momentumafter the collision (or explosion)’.
Law of Momentum: The applied resultant force acting on an object is equal to the rate ofchange of
the object’s momentumand this force is in the direction of the change inmomentum.
Chapter 12 End of Chapter Exercises
Forces and Newton’s Laws- [SC 2003/11] A constant, resultant force actson a body which can move freely in a
straight line. Which physical quantity will remain constant?
(a) acceleration
(b) velocity
(c) momentum
(d) kinetic energy - [SC 2005/11 SG1] Two forces, 10 N and 15 N, act at an angle at the same point.
10 N
15 N
Which of the following cannot be the resultant of thesetwo forces?
(a) 2 N
(b) 5 N
(c) 8 N
(d) 20 N- A concrete block weighing 250 N is at rest on an inclined surface atan angle of 20◦.
The magnitude of the normal force, in newtons,is
(a) 250
(b) 250 cos 20◦
(c) 250 sin 20◦
(d) 2500 cos 20◦