Question 190776
I'm assuming that you've been given the kinetic energy formula: {{{KE=(1/2)mv^2}}} where "KE" is the kinetic energy (think of it as the energy it has when it is moving), "m" is the mass, and "v" is the velocity



Note: the units for the three variables are:


KE: joules (j)

m: kilograms (kg)

v: meters per second (m/s)


the units in this problem are very important



First, take note that 4000 kg in scientific notation is written as {{{m=4*10^3}}} kilograms



Also, 1.8 MJ (1.8 megajoules) can be written as 1,800,000 joules, which is {{{1.8*10^6}}} joules. So the kinetic energy is {{{KE=1.8*10^6}}} joules.




{{{KE=(1/2)mv^2}}} Start with the given formula



{{{1.8*10^6=(1/2)(4*10^3)v^2}}} Plug in {{{KE=1.8*10^6}}} and {{{m=4*10^3}}}



{{{1.8*10^6=(2*10^3)v^2}}} Multiply {{{1/2}}} by {{{4*10^3}}} to get {{{2*10^3}}}



{{{(1.8*10^6)/(2*10^3)=v^2}}} Divide both sides by {{{2*10^3}}}.



{{{900=v^2}}} Divide



{{{v^2=900}}} Rearrange the equation



{{{v=sqrt(900)}}} Take the square root of both sides (we're only interested in the positive square root)



{{{v=30}}} Take the square root of 900 to get 30



So the velocity is 30 m/s