Physics question : Forces and Motion??

Question

a snail travelling 100km/h has stopped suddenly. If the deceleration is 10m/s/s, how long did it take the snail to stop?

a car acellerates from 12m/s - 72m/s in 30 seconds. What is its acceleration, and what was the distance travelled?

you dont have to answer my homework if you dont want to, but i just want to know how to get the answer because im confuzzled!

Answer 1

acelleration equals change in velocity over time.

a=(v-u)/t

so like, with the first question, you would take how fast the snail is going in the first place in meters per second (which is u in the equation), then take that away from 0 which you get because when the snail stops it has no velocity (thats v in the equation). You know that you're acceleration is -10 (negitive because its slowing down, not speeding up). So then you plug those numbers in, re-arrange the equation and work it out! you should get something like

t=(v-u)/a

t=(0-100)/-10

t=-100/-10

t=10

there you go! same thing goes for the second one, but the acceleration is positive, because you're going faster this time!    

Answer 2

Don't forget to convert 100km/h to m/s

100km/h=100*(1000m)/(3600s)=27.78m/s

so

t=(0-27.78)/(-10)=2.78s