The concept of work in physics is much more narrowly defined than the common use of the word. Work is done on an object when an applied force moves it through a distance. In our everyday language, work is related to expenditure of muscular effort, but this is not the case in the language of physics. A person that holds a heavy object does no physical work because the force is not moving the object through a distance. Work, according to the physics definition, is being accomplished while the heavy object is being lifted but not while the object is stationary. Another example of the absence of work is a mass on the end of a string rotating in a horizontal circle on a frictionless surface. The centripetal force is directed toward the center of the circle and, therefore, is not moving the object through a distance; that is, the force is not in the direction of motion of the object. (However, work was done to set the mass in motion.) Mathematically, work is W = F · x, where F is the applied force and x is the distance moved, that is, displacement. Work is a scalar. The SI unit for work is the joule (J), which is newton‐meter or kg m/s 2. i) When a body falls freely towards the earth, then its total energy: (a) increases (b) decreases (c) remains constant (d) first increases and then decreases ii. A car is accelerated on a levelled road and attains a velocity 4 times of its initial velocity In this process the potential energy of the car: (a) does not change (b) becomes twice to that of initial (c) becomes 4 times that of initial (d) becomes 16 times that of initial iii. In case of negative work the angle between the force and displacement is: (a) 0 (b) 450 (c) 900 (d) 1800 iv. An iron sphere of mass 10 kg has the same diameter as an aluminium sphere of mass is 3.5 kg. Both spheres are dropped simultaneously from a tower. When they are 10 m above the ground, they have the same: (a) acceleration (b) momenta (c) potential energy (d) kinetic energy v. A girl is carrying a school bag of 3 kg mass on her back and moves 200 m on a levelled road. The work done against the gravitational force will be (g =10 m s–2): (a) 6 ×103 J (b) 6 J (c) 0.6 J (d) zero -------------------------------------------------------------------------------------------------------------------------- More questions to be added shortly...