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# A car is moving at 100 km/hr.

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

### 3 Answers by Expert Tutors

Andre W. | Friendly tutor for ALL math and physics coursesFriendly tutor for ALL math and physics ...
5.0 5.0 (3 lesson ratings) (3)
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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.)
Brad M. | STEM Specialist plus Business, Accounting, Investment & EditingSTEM Specialist plus Business, Accountin...
4.9 4.9 (230 lesson ratings) (230)
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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 :)
Vivian L. | Microsoft Word/Excel/Outlook, essay composition, math; I LOVE TO TEACHMicrosoft Word/Excel/Outlook, essay comp...
3.0 3.0 (1 lesson ratings) (1)
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Hi Sierra;
Good to hear from you again.
I am assuming that ke is Kinetic Energy.
ke=(1/2)mv2
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.
Numerical answer only in mj to 3 decimal places