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:540 kJ

Step-by-step 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
`=(mv_i^2)/(2)-(mv_f^2)/(2)`

Energy dissipated
`=(1200* 30^2)/(2)`

Energy dissipated
`=540 kJ`

Answer 2

Energy dissipated = 540 kJ

Step-by-step explanation:

Energy dissipated = Change in kinetic energy

Initial velocity = 30 m/s

Mass, m = 1200 kg

`\texttt{Initial kinetic energy = }(1)/(2)mv^2=0.5* 1200* 30^2=540000J`

Final velocity = 0 m/s

`\texttt{Final kinetic energy = }(1)/(2)mv^2=0.5* 1200* 0^2=0J`

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

Energy dissipated = 540 kJ