<\/p>\n\n\n
Work is said to be done whenever a force acts on a body and the body moves through some distance in the direction of the force. Thus, work is done on a body only if the following two conditions are satisfied:<\/p>\n\n\n\n
(i) A force acts on the body.<\/p>\n\n\n\n
(ii) The point of application of the force moves in the direction of the force.<\/p>\n\n\n\n
Examples:<\/strong><\/p>\n\n\n\n Work is done when a horse pulls a cart, an engine pulls a train, a man goes up a hill, etc.<\/p>\n\n\n If a force acting on a body has a component in the direction of the displacement, then the work done by the force is positive.<\/p>\n\n\n\n when \u03b8 is acute, cos \u03b8 is positive. \u2234 W = Fs cos \u03b8 = a positive value<\/p>\n\n\n\n Examples:<\/strong><\/p>\n\n\n\n (i) When a body falls freely under gravity (\u03b8 = 0\u00b0), the work done by the gravity is positive.<\/p>\n\n\n\n (ii) When a horse pulls a cart, the applied force and displacement are in the same direction, the work done by the horse is positive.<\/p>\n\n\n\n (iii) When a gas filled in a cylinder fitted with a movable piston is allowed to expand, the work done by the gas is positive, because the force due to gas pressure and displacement act in the same direction.<\/p>\n\n\n\n (iv) When a spring is stretched, both the stretching force and the displacement act in the same direction. So, work done is positive.<\/p>\n\n\n If a force acting on the body has a component in the opposite direction of displacement, the work done is negative. As shown in Fig. 6.4, when \u03b8 is obtuse, cos \u03b8 is negative.<\/p>\n\n\n\n \u2234 W = Fs cos \u03b8 = a negative value<\/p>\n\n\n\n Examples:<\/strong><\/p>\n\n\n\n (i) When a body slides against a rough horizontal surface, its displacement is opposite to the force of friction. The work done by the friction is negative.<\/p>\n\n\n\n (ii) When brakes are applied to a moving vehicle, the work done by the braking force is negative. This is because the braking force and the displacement act in opposite directions.<\/p>\n\n\n\n (iii) When a body is lifted, the work done by the gravitational force is negative. This is because the gravitational force acts vertically downwards while the displacement is in the vertically upward direction.<\/p>\n\n\n\n (iv) When a positive charge is moved towards another positive charge, the work done by the force of repulsion (between them) is negative because displacement s is\u00a0in the opposite direction of repulsive force.<\/p>\n\n\n Work done by force is zero if the body gets displaced along a direction perpendicular to the direction of the applied force. Also, the work done is zero if F<\/em><\/strong>\u00a0or S<\/em><\/strong>\u00a0or both are zero.<\/p>\n\n\n\n Examples:<\/strong> <\/p>\n\n\n\n (i) For a body moving in a circular path, the centripetal force and displacement are perpendicular to each other. So, the work done by the centripetal force is zero.<\/p>\n\n\n\n (ii) When a coolie walks on a horizontal platform with a load on his head, he applies a force on it in the upward direction equal to its weight. The displacement of the load is along the horizontal direction. Thus, the angle between F <\/em><\/strong>and S<\/em><\/strong>\u00a0is 90\u00b0. So, W = Fs cos 90\u00b0 = 0 i.e., the work done by the coolie on the load is zero.<\/p>\n","protected":false},"excerpt":{"rendered":" What is Work? Work is said to be done whenever a force acts on a body and the body moves through some distance in the direction of the force. Thus, work is done on a body only if the following two conditions are satisfied: (i) A force acts on the body. (ii) The point of … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"_links":{"self":[{"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/posts\/100"}],"collection":[{"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/comments?post=100"}],"version-history":[{"count":1,"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/posts\/100\/revisions"}],"predecessor-version":[{"id":101,"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/posts\/100\/revisions\/101"}],"wp:attachment":[{"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/media?parent=100"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/categories?post=100"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/tags?post=100"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Nature of Work Done in Different Situations<\/h3>\n\n
Positive work: <\/strong><\/h4>\n\n\n
Negative work<\/strong>:<\/h4>\n\n\n
Zero work<\/strong>: <\/h4>\n\n\n