A car is running at a speed of $15 k m h^{- 1}$ while another similar car is moving at a speed of $30 k m h^{- 1}$ . Find the ratio of their kinetic energies.

4 : 1

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1 : 2

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1 : 4

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1 : 1

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Solution

The correct option is B $1 : 4$
It is like one car is moving with $v$ speed and other with $2 v$ speed because one is $15 k m / h$ and other is $30 k m / h$ .
$K . E = 0.5 \times m \times v^{2}$
$K . E (1 s t) = 0.5 \times m \times v^{2}$
$K . E (2 n d) = 0.5 \times m \times (2 v)^{2}$
Hence the ratio is $0.5 \times m \times v^{2} : 0.5 \times m \times (2 v)^{2} = 1 : 4$
Hence the ratio is $1 : 4$ .

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A car is running at a speed of 15kmh−1 while another similar car is moving at a speed of 30kmh−1. Find the ratio of their kinetic energies.

The correct option is B 1:4It is like one car is moving with v speed and other with 2v speed because one is 15 km/h and other is 30 km/h .K.E=0.5×m×v2K.E(1st)=0.5×m×v2K.E(2nd)=0.5×m×(2v)2Hence the ratio is 0.5×m×v2:0.5×m×(2v)2=1:4Hence the ratio is 1:4.

A car is running at a speed of $15 k m h^{- 1}$ while another similar car is moving at a speed of $30 k m h^{- 1}$ . Find the ratio of their kinetic energies.