(i) Define kinetic energy of an object. Can kinetic energy of an object be negative? Give reason.
(ii) A car weighing 1200 kg is uniformly accelerated from rest and covers a distance of 40 m in 5 s. Calculate the work, the car engine had to do during this time.
(i) The energy possessed by a body by virtue of its motion is called its kinetic energy.
No, the kinetic energy of an object cannot be negative because both m and v are always positive and
KE = 1/2 m ${{v}^{2}}$
(ii) Given, m = 1200 kg, s = 40 m, t = 5 s, u = 0, W = ?
We know that , W = Fs = mas
or S= ut + 1/2 a${{t}^{2}}$
40 = 0 x t +1/2 x a x 5 x 5
a = 40 x 2 /25 = 3.2 m
W = Fs = mas
1200 x 3.2 x 40 = 156300J