Question

# A system consists of two cubes of masses m1 and m2 respectively connected by a spring of force constant k. The force (F) that should be applied to the upper cube for which the lower one just lifts after the force is removed, is

A
m1g
B
m2g
C
(m1+m2)g
D
m1+m2m1+m2g

Solution

## The correct option is D (m1+m2)gInitially in equilibrium F+m1g=kxi           (xi=initial compression) ∴       xi=F+m1gk          ...(1) Let xf be the elongation in spring when lower block just lifts.  Then,  kxf=m2g    or   xf=m2gk     ....(2) Now from conservation of mechanical energy, increase in gravitational potential energy of m1 = decrease in elastic potential energy of spring. ∴     m1g(xi+xf)=12k(x2i−x2f) substituting the values of xi and xf from Eqs. (1) and (2), we get F=(m1+m2)gCo-Curriculars

Suggest Corrections

2

Similar questions
View More

People also searched for
View More