Answer
(a) The maximum thrust the engines can have is $1.10\times 10^8~N$.
(b) $F_N = 5\times ~weight$
(c) The shortest time to reach the speed of sound is 8.44 seconds.
Work Step by Step
(a) $\sum F = ma$
$F_{thrust} - mg = m(4g)$
$F_{thrust} = 5mg = (5)(2.25\times 10^6~kg)(9.80~m/s^2)$
$F_{thrust} = 1.10\times 10^8~N$
The maximum thrust the engines can have is $1.10\times 10^8~N$.
(b) $\sum F = ma$
$F_N -mg = m(4g)$
$F_N = 5mg = 5\times ~weight$
(c) We can find the time to reach the speed of sound.
$t = \frac{v-v_0}{a} = \frac{331~m/s-0}{(4)(9.80~m/s^2)}$
$t = 8.44~s$
The shortest time to reach the speed of sound is 8.44 seconds.
