Solar cells are used to trap sunlight energy (light energy) and convert it to electric energy for domestic and other purposes.
Use the first kinematic formula
Vf = Vi + at
10 = 0 + 1(t)
10 = t
10 seconds
Acceleration=force/mass=28/(10+4)=2m/s^2
force10kg=ma=10*2
force4kg=ma=(10*2)=20
the4 kg is pushing against the 10kg block
vf=vi+at
-10=20*28/14 * t
t=30/2=15sec
i hope this can help you.
