A 4000kg lorry is moving with a constant velocity of 30ms^-1 . The driver of the lorry then decelerates with 0.5ms^-1 . Calculate the energy loss while the driver decelerates. Show working please.

Question

anonymous · Answer

the deceleration for 10 s.

anonymous · Answer

m= 4000kg
u= 30m/s
v=0m/s
a=-0.5m/s^2

$$v^2-u^2=2.a.s$$

put the values and get 's'..

s=900m

then,
$$W= m.a.s$$

'W' is the amount of work done to stop the lorry=Energy loss

now get the answer.. :)

anonymous · Answer

-tive value indicates energy loss..

anonymous · Answer

$$v=u+at$$$$v=30+(-0.5)(10)$$$$v=25$$ energy lost=$$0.5mv^2 - 0.5mu^2$$=$$0.5(4000)(25^2 - 30^2) = -550000J$$

anonymous · Answer

@glgan1 You got the answer right .
Why do u need to find v? i supposed the final velocity is 0?
I dont understand  this part?
What formula is that?
energy lost=
0.5mv2−0.5mu2

anonymous · Answer

sorry i had not noticed the tym given...

anonymous · Answer

nope. the final velocity isn't 0. it doesn't state that it stops. it just says that it decelerates for 10s so we can't assume it's stopped. 0.5mu^2 is the initial kinetic energy for the lorry and 0.5mv^2 is the final kinetic energy of the lorry which is after deceleration.

anonymous · Answer

@rahulchatterjee Its alright. :)

anonymous · Answer

@glgan1 Thank u

anonymous · Answer

you're welcome.