Please dont solve the problem since i have the solution as u can see, i only wan

Question

Please dont solve the problem since i have the solution as u can see, i only want to know why the normal and friction forces do not work while the weight does work? I know that force does work when it moves through a displacement in the direction of the force . So here the motion is rotation its not going upward or downward . Its is swinging so its moving left and right so as i understand the weight and normal forces should not work while the friction should do work . Can u explain how can i change what i have understood? When do actually a force work? 466 CHAPTER 18 PLANAR KINETICS OF A RIGID BoDY: WORK AND ENERGY EXAMPLE 18.4 The 700-kg pipe is equally suspended from the two tines of the fork lif shown in the photo. It is undergoing a swinging motion such that whe e 30° it is momentarily at rest. Determine the normal and fri forces acting on each tine which are needed to support the pipe at the instant ?=0°. Measurements of the pipe and the suspender are shown in Fig, 18-14a. Neglect the mass of the suspender and the thickness of the pipe. 0.4 m 0.15 m Fig. 18-14 SOLUTION We must use the equations of motion to find the forces on the tines since these forces do no work. Before doing this, however, we will apply the principle of work and energy to determine the angular velocity of the pipe when 0

Explanation / Answer

Since work done W = F.S = Fs Cos (theta)

Here theta be the angle between acting force and displacement due to this force. If theta = 0° ... Cos0° = 1

Then work done will be maximum.

Here in case of normal force and frictional for.... There is no displacement along the force . Here displacement takes place in perpendicular to both... Hence theta = 90°

And hence ... Cos(theta) = 0... Hence work done is zero in both case. ....

Thank you.

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