Video narration
Net Work zero hai, to Kinetic Energy same rahegi, yani speed same rahegi. Iska matlab hamesha motion ruk gaya, aisa nahin hai. Direction badal sakti hai, jaise circular motion mein; bas speed change nahin hoti. Ek chhota JEE-style example lo. Ek 2 kg block ki initial speed 3 m/s hai. Us par sabhi forces ka mila hua Net Work 16 J hai. Final speed kya hogi? Seedhe theorem lagao: W_net = K_f - K_i. Initial Kinetic Energy, 1/2 x 2 x 3 squared, yani 9 J. Net Work positive 16 J hai, isliye final Kinetic Energy 9 + 16 = 25 J. Ab 1/2mv2 = 25. Mass 2 kg hai, to 1/2 x 2 x v2 = 25, yani v2 = 25. Final speed 5 m/s. Block tez hua, kyonki total work ne uski Kinetic Energy badhai. Alag-alag force ke peechhe bhagne ki zarurat nahin thi; unka sum pehle hi 16 J diya hua tha. To opening wale bicycle sawal ka jawab yahi hai: pedal aage ka positive work deta hai, isliye speed badhti hai; brake motion ke opposite negative work deta hai, isliye speed ghat ti hai. Kyonki Net Work hi Kinetic Energy ko change karta hai.