Force = mass x acceleration
force = 2500kg x (20m/s / 10m/s)
force = 2500kg x 2m/s^2
force = 5000kg m/s^2 = 5kN
i hope this is right (^^)
A mirror is opaque you can not see through it but you can see a reflection within it
We Know, Power = Energy/Time
Substitute the known value. which is P = 350 watt, & T = 30 sec
350 = E/30
E = 350 * 30
E = 1050 Joules.
So, your answer is 1050 Joules.
Hope this helps! Keep studying!