Question

How much energy is dissipated in braking a 1200-kg car to a stop from an initial speed of 30 m/s?

Answer 1

Answer:

Energy dissipated = 540 kJ

Explanation:

Energy dissipated = Change in kinetic energy

Initial velocity = 30 m/s

Mass, m = 1200 kg

$\texttt{Initial kinetic energy = }\frac{1}{2}mv^2=0.5\times 1200\times 30^2=540000J$

Final velocity = 0 m/s

$\texttt{Final kinetic energy = }\frac{1}{2}mv^2=0.5\times 1200\times 0^2=0J$

Energy dissipated = Change in kinetic energy = 540000-0 = 540000J

Energy dissipated = 540 kJ

Answer 2

Answer:540 kJ

Explanation:

Given

mass of car $m=1200 kg$

Initial speed of car $v_1=30 m/s$

Final speed of car $v_2=0 m/s$

Energy dissipated=change in kinetic Energy

Energy dissipated=Initial Kinetic Energy-Final Kinetic Energy

Energy dissipated$=\frac{mv_i^2}{2}-\frac{mv_f^2}{2}$

Energy dissipated$=\frac{1200\times 30^2}{2}$

Energy dissipated$=540 kJ$