When a force is applied on a car of 100 kg by its engine; then its velocity increases from 54 km/h to 60 km/h; find the work done by the force. a. 200 kJ B. 20 kJ C. 2 kJ D. 120 kJ
To solve, apply the work-energy theorem. The formula is:
`W=Delta KE = 1/2m(v_f^2-v_i^2)`
`W` - work done in Joules (J)
`Delta KE` - change in kinetic energy,
`m` - mass of object in kg,
`v_i` - initial velocity in m/s and
`v_f` - final velocity in m/s
So before subsitituting the values, convert the unit of velocities from km/h to m/s.
`v_i=54 (km)/hxx(1h)/(3600s)xx(1000m)/(1km)=15 m/s`
Then, plug-in m = 100, v_i = 15 and v_f=16.67 to the work-energy formula.
Then, divide it by 1000 to convert to kiloJoules, kJ.
Among the given choices, the nearest answer is (C) 2kJ.