At what speed does.....

Question

At what speed does a 1100 kg compact car have the same kinetic energy as a 1.9×10^4 kg truck going 25 km/hr?

Express answer in two significant figures.

Answer 1

KE = 1/2 mass*(velocity^2)

so just set the two equal

(1/2)(1.9E4 kg)(25000/3600 m/s) = (1/2)(1100 kg)(velocity of car ^2)

Answer 2

m = 1100kg

M = 1.9E4kg

V = 25km/hr

v = ??

KE = ½mv² = ½MV²

v² = MV²/m

v = V √(M/m) = 25 √(1.9E4/1100) = 103.9 = 100 km/hr .....(2sf)

there is no need to convert units, (unless it asks for m/s)

kg, km & hrs works just as good as SI units, the important thing is that you choose a particular set of units and then stick to them

.,.,

Answer 3

Hey!

What you want to use is the KE formula 1/2mv^2

Here you want 1/2m1(v1)^2 to equal 1/2m2(v2)^2

m1 is for the mass of the compact car and m2 is for the mass of the truck

v1 is speed of compact car and v2 is speed of the truck

u do 1/2(1100)(v1)^2=1/2(1.9X10^4)(25)^2

u crunch the numbers and solve for v1 the speed of the compact car!

This answer will come out in km/hr and so u might need to convert to m/s as needed.