See below?

a) A car of mass 850 kg is travelling at a constant speed of 12m/s. Calculate the car's store of kinetic energy. Give your answer in standard form expressed to 2 significant figures.
b) The car now accelerates increasing its store of kinetic energy by a factor of 2. (I don't understand what factor of 2 means) Calculate the car's speed. Give your answer to 2 significant figures.

1 Answer
sjc
Jul 23, 2017

(a) #6.1xx10^4J" "#2 sig fig

(b) #v=17ms^(-1)" "2 " sig fig"#

Explanation:

#Kinetic energy is calculated by teh formula

#KE=1/2mv^2#

where

#m=mass#

#v=velocity.#

#(a)" "KE=1/2xx850xx12^2=61200J#

In standard form to 2 sig figs

#6.1xx10^4J#

(b) increased by SF 2

#KE=2xx61200=122400J#

to find its velocity

#1/2xx850xxv^2=122400#

#v^2=(2xx122400)/850#

#v^2=288#

#v=sqrt288=12sqrt2ms^(-1)#

#v=16.97056275ms^(-1)#

#v=17ms^(-1)" "2 "sig fig"#

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