Answer:
Explanation:
Let fuel is released at the rate of dm / dt where m is mass of the fuel
thrust created on rocket
= d ( mv ) / dt
= v dm / dt
this is equal to force created on the rocket
= 220 dv / dt
so applying newton's law
v dm / dt = 220 dv / dt
v dm = 220 dv
dv / v = dm / 220
integrating on both sides
∫ dv / v = ∫ dm / 220
lnv = ( m₂ - m₁ ) / 220
ln4000 - ln 2500 = ( m₂ - m₁ ) / 220
( m₂ - m₁ ) = 220 x ( ln4000 - ln 2500 )
( m₂ - m₁ ) = 220 x ( 8.29 - 7.82 )
= 103.4 kg .
Kinetic energy = momentum^2 / 2 x mass
Mass = (momentum^2/ Kinetic energy) / 2
Mass = (25^2 / 275) / 2
Mass = 1.136 kg.
momentum = mass x velocity
velocity = mass / momentum
velocity = 1.136 / 25
velocity = 0.04544 m/s
I think the correct answer from the choices listed above is option B. When calculating the power bill, power companies use kilowatt-hours. This unit is a derived unit of energy equal to 3.6 MJ. If energy is being transmitted or used at a constant rate (power) over a period of time, the total energy in kilowatt-hours is the product of the power in kilowatts and the time.
In both cases less energy is required
But comparetively Mg require more energy than K
Let's see the electron configuration of Both
- [Mg]=1s²2s²2p⁶3s²=[Ne]3s²
- [K]=1s²2s²2p⁶3s²3p⁶4s¹=[Ar]4s¹
K has only one valence electron so very less ionization enthalpy so less energy required
Mg has 2 so more IE hence more energy required
