Question

A car is moving with a velocity of 36 km h.
Express this velocity in m/s. What velocity will
double its kinetic energy? [Ans. 10 ms.14.14 ms]​

Answer 1

velocity=36km/h

=(36*1000 m) /(3600 seconds)

=10 m/s

The kinetic energy

$\frac{1}{2} m {v}^{2}$

Let for velocity u the kinetic energy is doubled

So

$\frac{1}{2} m {u}^{2} = 2 \times \frac{1}{2} m {v}^{2} \\ or \: {u}^{2} = 2 {v}^{2} \\ or \: u = \sqrt{2} v$

So, u=1.414 *10=14.14 m/s

Answer 2

Answer:

for converting value of km per hour into m per sec we need to multiply by 5/18 .

hence 5/18×36=10m/sec.

as mass is constant but velocity variates by double

then kinetic energy k1=1/2mv1square

m=2k/v1

and kinetic energy k2= 1/2mv2 square

put the value of m in 2

then , we get

v2=2k/m

v2=2k×v1/2k

v2 = 36/2

v2 = 18 km/hr