89 Mega Joules can also be expressed as _____
a) 8900 Joules
b) 89000000 Joules
c) 89000 Joules
d) 890000 Joules

Explanation

Both upper block andlower block will have acceleration `2m/s^2`

`R_1=mg F=mu R_1-T=0`
`rarr T-muR_1=0`
`and `F--mu mg =T` …..ii
`rarr T=mu mg`
Putting `T=mu mg`
`F=mu mg +mu mg = 2mu mg`
b. `2F=T-mumg -ma`
=0.........i
`T-ma-mu mg =0 [:.R=mg]`
`rarr T=ma+mumg`
Putting value of T in i. we have
`2F-Mamu mg +mu mg-ma=0`
Putting `F=2mumg`
2(2mumg)-2mumg=a(M+m)`
`rarr4mu mg-2mumg=a(M+m)`
`rarr a=(2mu mg)/(M+m)`
Both blocks move with this acceleration a in opposite direction.