Question

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.

Answer 1

(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"`