Question

the mass of cyclist together with the bike is 90 kg calculate the increasing kinetic energy pte speed increased from 6 km per hour to 12 km per hour

Answer 1

Total mass of the system (cyclist and bike), M=mc+mb=90 kg

Initial velocity of the system, u=6.0 km/h=1.666 m/sec

Final velocity of the system, ν=12 km/h=3.333 m/sec

From work-energy theorem, we have:
Increase in K.E.=12Mν2−12mu2=1290×(3.333)2−12×90×(1.66)2=499.4−124.6=374.8=375 J

Answer 2

Answer:

The mass of the cyclist together with the bike is 90 kg. The increasing kinetic energy when speed increased from 6 km per hour to 12 km per hour is 375 J.

Explanation:

Given,

The total mass (m)   =  90 kg

Initial speed  $\left(V_{i}\right)$      =  6 km/hr = $6 \times\frac{5}{18} =\ 1.6666 \ m/s$

Final speed  $\left(V_{f }\right)$      =  12 km/hr =  $12 \times\frac{5}{18} =\ 3.3333 \ m/s$

We have the expression for Kinetic energy (K.E) as,

$\mathrm{K} . \mathrm{E}=\frac{1}{2} m V^{2}$

So the change in K.E will be,

$\Delta \mathrm{KE}=\frac{1}{2} \mathrm{~m}\left(\mathrm{~V}_{\mathrm{f}}^{2}-\mathrm{V}_{\mathrm{i}}^{2}\right)$

          =  $\frac{1}{2} \times 90 \times\left(\left\\3.333^{2}-\left\\1.6666^{2}\right)$

          =  $374.9999$ J

          ≈   375 J

Ans:

The Increase in kinetic energy  = 375 J