Question

A 2000 kg car has a speed of 12 m/s. the car hits a tree. The tree does not move, and the car comes to rest, find change in energy? Give the answer in terms of scientific notation

Answer 1

change in energy is due to kinetic energy
KE=1/2m(v^2 -u^2)
KE= 1/2*2000(0^2-12^2)
     =1000*(-144)
     =-144KJ

Answer 2

Initial energy = 0.5mu²
= 0.5 × 2000 kg × (12 m/s)²
= 1.44 × 10⁵ Joule

Final energy = 0.5mv²
= 0 Joule ……[∵ It came to rest]

Change in energy = Initial energy - Final energy
= 1.44 × 10⁵ Joule - 0 Joule
= 1.44 × 10⁵ Joule

Change in energy is 1.44 × 10⁵ Joules