Question

Numericals:-A bike moving at a speed of 36km per hour has kinetic energy 9800J . Find the mass of the bike.
please answer if fast tomorrow is my exa​

Answer 1

Answer:

Mass of the trolley, M=200kg

Speed of the trolley, v=36km/h=10m/s

Mass of the boy, m=20kg

Initial momentum of the system of the boy and the trolley

=(M+m)v

=(200+20)×10

=2200kg m/s

Let v

′

be the final velocity of the trolley with respect to the ground.

Final velocity of the boy with respect to the ground =v

′

−4

Final momentum =Mv

′

+m(v

′

−4)

=200v

′

+20v

′

−80

From the conservation of linear momentum:

Initial momentum= Final momentum

2200=220v

′

−80

∴ v

′

=2280/220=10.36m/s

Length of the trolley, l=10m

Speed of the boy, v

′′

=4m/s

Time taken by the boy to run, t=10/4=2.5s

∴ Distance moved by the trolley =v

′′

×t= 10.36×2.5=25.9m

Answer 2

Answer:

196kg.

Explanation:

Speed = 36km/h.

Convert km/h into m/s

$\rm{ \dfrac{5}{18} \times 36} = 5 \times2=10m/s.$

Kinetic Energy = 9800J.

Mass = ?

$\bf{E_K = \dfrac{1}{2} \times mv²}$

Substitute known values in the formula.

$\rm:\implies{9800= \dfrac{1}{2}×m(10)²} \\ \\ \\\rm:\implies{9800=} \frac{1}{2} \times m×100 \\ \\ \\\rm:\implies{9800=50m} \\ \\ \\\rm:\implies{50m=9800} \\ \\ \\ \rm:\implies{m= \frac{9800}{50} }\\ \\ \\\bf \therefore{Mass=196kg.}$

Hence, mass of the bike is 196kg.