Question

Two masses of 10kg and 20kg respectively are connected by a massless spring. A force of 200N acts on the 20kg mass. At the instant the 10kg mass has an acceleration 12m/s² towards right. What will be the acceleration of 20kg mass at at this instant?

Answer 1

For 20kg mass equation for net force=mass*acceleration is 200-kx=20*a

where 'kx' is spring force and 'a' is the acceleration of 20kg mass.

equation for 10kg mass

kx=10*12=120N

SO we know the value of kx, substitute that back in the first equation
200-120=20*a.
a = 4m/s
acceleration is 4m/s