Question

How much work must be done to stop a 900-kg car traveling at 106 km/h?(Hint: You will need to convert the speed first.)Answer: ___________ J (round to the nearest whole number)

Answer 1

The work needed to stop an object is equal to the kinetic energy of the object:

`K=(1)/(2)mv^2`

Write the speed in meters per second using the fact that 1m/s=3.6km/h. Then, the work needed to stop the car is:

`W=(1)/(2)(900kg)\left(106(km)/(h)*(1(m)/(s))/(3.6(km)/(h))\right)^2=390,138.88...J`

Therefore, the work that must be done to stop the car is approximately 390,139J.