Question

a driver shifts into neutral when her 1200 kg is moving at 80 km/h and finds the speed has dropped to 65 km/h 10 s later . what was the average drag force acting on the car? ...?

Answer 1

Drag is a force acting opposite to the relative motion of any object moving. It can be calculated as follows:

vi = (80km/hr) (1hr / 3600sec) (1000m/1km) = 22.2 m/sec

vf= (65km/1hr) (1hr/3600sec) (1000m/1km) = 18.06 m / sec
a=vf−vi / tf−ti = 18.06m/s−22.2m/s / 10sec−0sec= −0.414msec2

F = ma = 1200kg×−0.414ms2 = −496.8N