A spring has a spring constant of 800 N/m. How much work must be done to stretch the spring 0.4 m from its unstretched position? A. 64.0 J
B. 160.0 J
C. 320.0 J
D. 640.0 J

A. 64.0 J

Explanation:

Given parameters:

Spring constant  = 800N/m

Extension  = 0.4m

Unknown:

Work done  = ?

Solution:

The work done in a string is given as:

         Work done  = x 800 x 0.4²   = 64J

d

explanation:

v=uf/(u-f)

= 5.10/(5-10) convex lens has positive focal length

=50/-5

=-10 cm (formed at other side)

answer(20) psi;