An aircraft of 2 metric tonnes uses 800 kilojoules kinetic energy to make an emergency stop. Its brakes apply a force of 10 kiloNewtons. What distance does it travel before it comes to a stop?
- 40m.
- 8 m.
- 80m.
Explanation
The braking force does work equal to the kinetic energy dissipated: work = force x distance. Rearranging, distance = energy / force = 800 000 J / 10 000 N = 80 m. The aircraft's mass is not needed here because the energy is already given.
Azfar asking:
I need some explanation for this..i got the answer 2metres
Community Comments (5)
D
dimky Posts: 514 07.11.2013 / 20:08
Hey!
Could you please show your calculations?
Could you please show your calculations?
A
Azfar Posts: 3 07.11.2013 / 20:17
sorry..i have already got the right answer..my bad..
from the kinetic equation, 1/2 mv^2..i got the velocity 28.28 m/s..
from the force equation, F= ma..i got the acceleration 5ms^-2..
the distance is found out using v^2=u^2 +2as which is 80m.. this is the correct method right?didnt thought of it at first.
from the kinetic equation, 1/2 mv^2..i got the velocity 28.28 m/s..
from the force equation, F= ma..i got the acceleration 5ms^-2..
the distance is found out using v^2=u^2 +2as which is 80m.. this is the correct method right?didnt thought of it at first.
D
dimky Posts: 514 07.11.2013 / 20:24
It is possible to calculate much simplier.
Energy = Force * Distance, so
800000 KJ = 10000 KN * Distance, so
Distance = 800000 / 10000 = 80
:)
Energy = Force * Distance, so
800000 KJ = 10000 KN * Distance, so
Distance = 800000 / 10000 = 80
:)
T
tsukiyo92 Posts: 13 15.07.2014 / 06:16
aw... nice thought, azfar. I used work done formula first, after that only saw your calculation.
J
Jordi Posts: 198 14.06.2020 / 16:40
dimkys way is easier with a smaller probability for mistakes.
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