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A car is moving at 100 km/hr.

its mass is 950 kg. find it's ke.
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3 Answers

KE = ½mv²,
where v is in m/s.
v= 100 km/h = 27.8 m/s
KE = ½(950kg)(27.8m/s)²=367,000 J
(I'm assuming 3 significant digits, though it could be just 2 or 1.)
Hey Sierra -- 950kg moving 100km/hr ... V is 100m/3.6s ... KE= 0.5mV*V ...
KE= 0.5(950)100(100)/(3.6*3.6) ~ 480E4/(36*0.36) ~ 40E4/(3*0.36) ~ 400kJ - 8% ...
KE ~ 400 - 32 ~ 370kJ ... Regards :)
Hi Sierra;
Good to hear from you again.
I am assuming that ke is Kinetic Energy.
ke=(1/2)(950 kg)(100 km/hour)2
ke=(1/2)(950 kg)(10000 km2/hour2)
ke=4750000 kg-km2/hour2


ke=4750000 kg-km2/hour2
Do you need to convert to seconds?...
ke=[4750000 kg-km2/hour2][(1 hour)2/(360 sec)2]
ke=13194 kg-km2/sec2
Do you need to convert to meters?...
ke=[13194 kg-km2/sec2][(1000 m)2/(1 km)2]
ke=1319400 kg-m2/sec2
Yes, you should convert to meters/second, because a joule is defined as 1 J = 1 kg *m²/s²
Good point!
But she did not say she need Standard Units.
Then please use Andre's answer.
I apologize if I caused any confusion.
You're doing great, Vivian! And remember, 1 hour = 3600 seconds. :)