Question

A boy pulls a table along the floor of a room.
(a) Name the forces acting on the table
(b) Which of these forces perform positive work?
(c) Which of these forces perform negative work?​

Answer 1

Given:

A boy pulls a table along the floor of a room.

To find:

• Name the forces acting on the table
• Which of these forces perform positive work?
• Which of these forces perform negative work?

Solution:

1. The various forces acting on the table are as follows:

• Applied force (F)
• Frictional force (f)
• Gravitational force (mg)
• Normal reaction force (N)

$\setlength{\unitlength}{1mm}\begin{picture}(5,5)\put(0,0){\framebox(15,15){\sf{m}}}\put(-20,-0.1){\line(1,0){55}}\multiput(-19,0)(3,0){19}{\qbezier(0,0)(-1,-1)(-2,-2)}\put(15,7.5){\vector(1,0){15}}\put(7.5,0){\vector(0,-1){15}}\put(4,-20){\sf{mg}}\put(7.5,15){\vector(0,1){15}}\put(6.3,31.5){\sf{N}}\put(0,0.2){\vector(-1,0){15}}\put(-17,1.3){\sf{f}}\put(32,6){\sf F}\end{picture}$

2. The force performing positive work is APPLIED FORCE , because the angle between Force and displacement vector is 0°. Hence work is positive.

3. The force performing negative work is FRICTIONAL FORCE, because the angle between force and displacement is 180°, hence work is negative.

Hope It Helps.