posted by cassandra .
a 21.2 kg mass attached to a spring scale rests on a smooth, horizontal surface. the spring scale, attached to the front end of a boxcar, reads T=35.6N when the car is in motion. If the spring scale reads zero when the car is at rest, determine the acceleration of the car, when it is in motion as indicated above
a=F/m = 35.6/21.2=1.68 m/s²