Car A has a mass of 1000kg and a speed of 60 km/h, and car B has a mass of 2000 kg and a speed of 15 km/h. The kinetic energy of Car a is:
a) half that of car B
b) equal to that of car B
c) eight times that of car B
d) four times that of car B
2007-05-21 06:39:17 · 8 answers · asked by Anonymous in Science & Mathematics ➔ Physics
KE = 1/2 mv^2
the speed of the first 1 is 4 times the speed of the second one, so it KE will be 16 times larger becasue the speed is squared. Hoever, the mass of the second one is twice the mass of the first 1, so that will halve the KE.
Therefore the KE of car A is 8 times that of car B. Choice C
2007-05-21 06:49:17 · answer #1 · answered by Anonymous · 0⤊ 0⤋
If KE=1/2(.5)*m/v^2 it's basically just a simple substitution and check problem.
A) .5*1000*60^2 = 1,800,000
B) .5*2000*15^2 = 225000
1800000/225000 = 8 so the answer is C.
* *
Not sure whether or not you needed to convert kph -> mps but in case you did it's a simple conversion method (5/18).
So, 60(5/18) = 16.67 (approx)
& 15(5/18) = 4.167 (approx)
A) .5*1000*16.67^2 = 138944.45
B) .5*2000*4.167^2= 17363.9 (approx)
Thus, 138944.45/17363.9 = Approximately 8 (8.0019...) times that of car B. Answer C in both variations.
2007-05-24 13:02:20 · answer #2 · answered by Ghosted 1 · 0⤊ 0⤋
Kinetic Energy = mv^2/2
Since we are dealing with a ratio we can ignore the factor 1/2, since (1/2)/(1/2) = 1. The answer is also independant of the units. Anyway...
A/B = (1000x60*60)/(2000*15*15) = 8
So the answer is c).
2007-05-21 13:56:45 · answer #3 · answered by Anonymous · 0⤊ 0⤋
KE = 1/2 mv^2
Car A has KE of 1000 times 3600/2
Car b has KE = 2000 times 225/2
You need C)
2007-05-21 13:52:45 · answer #4 · answered by rosie recipe 7 · 0⤊ 0⤋
All of the following is in your physics book, if you'd trouble yourself to open it and actually study.
Ke is kinetic energy
m is mass
v is velocity
They are related by a simple expression
Ke = mv²/2
If you can't figure out how to do the arithmetic, quite wasting space in the classroom and the teachers time.
HTH
Doug
2007-05-21 13:46:52 · answer #5 · answered by doug_donaghue 7 · 0⤊ 2⤋
Car A
v = 60 km/h = 16.67 m/sec
KE = 0.5 * m * v^2
KE = 0.5 * 1000kg * (16.67 m/sec)^2
KE = 138944.45 J
Car B
v = 15 km/h = 4.167 m/sec
KE = 0.5 * m * v^2
KE = 0.5 * 2000 kg * (4.167 m/sec)^2
KE = 17363.9 J
138944.45 J / 17363.9 J = 8
the answer is C
2007-05-21 13:43:51 · answer #6 · answered by mark r 4 · 0⤊ 1⤋
Substitute into your equations and you'll find the answer.
2007-05-21 13:45:25 · answer #7 · answered by poison_for_food 2 · 0⤊ 0⤋
c
2007-05-25 12:17:57 · answer #8 · answered by johnandeileen2000 7 · 0⤊ 0⤋