Question

W = F*scos Φ i don't understand what is cos Φ​

Answer 1

Answer:

it is the angle between the body and the direction in which the object move you don't need to take Φ instead you can take any sign like α βor A B C whatever you need

Explanation:

suppose you carry a bag and walking straight in this phenomenon your direction is same as the direction of bag in this case the angle becomes zero and you well know that cos 0 is 1 so in this case your work done is maximum

2- in second case suppose you carry that bag perpendicular to the direction in which you move so in this case the angle becomes 90 and cos 90 is 0 so the work done is 0