Question

A car is mving with a speed of 15km/h and another identical car at speed 30 km/h. Compare their kinetic energy

Answer 1

Answer:

1/4

Explanation:

According to the given question,

m1 = m2 i.e, they are identical hence they must have same mass.

v1 = 15 km/h

v2 = 30 km/h

And we are asked to compare the kinetic energy of both.

We know,

• k.E. = 1/2 mv^2

Where k.E = Kinetic energy

v = velocity and m = mass

Thus,

• K.E1 = 1/2 m1×v1^2--------1)

• K.E2 = 1/2 m2× v2^2----------2)

So, Dividing the thegiven equation;

• k.E1/K.E2 = (m1/m2)×(v1/v2)^2

• K.E1/K.E2 = (v1/v2)^2

[As m1 = m2, they got cancelled out]

• K.E1/K.E2 = (15/30)^2

[By putting the values we get]

• K.E1/K.E2 = (1/2)^2

• K.E1/K.E2 = 1/4

• K.E2/K.E1 = 4

Thus we can say that,

• K.E2 = 4×K.E1

It means that kinetic energy of the 2nd car is 4 times of first car.

Answer 2

Explanation:

the second car is having greater kinetic energy and it's speed is more than the first car. no calculations needed.

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