Question

A force of 2170 N is needed to bring a car

moving at 24.3 m/s to a halt in 17.2 s.
What is the mass of the car?
Answer in units of kg.

Answer 1

It's implying that a constant force was applied throughout, which also means that there was a constant, negative acceleration. Because of that, the deceleration is equal to the change in velocity (-24.3 m/s) divided by the time (17.2 s):
`(-24.3 m/s)/(17.2 s)`=-1.41279 m/s^2. The force is technically negative because it is causing a negative acceleration. Because F=ma: -2170kg m/sec^2=-(-1.41279 m/sec^2)m. m=
`(-2170 kg m/s^2)/(-1.41279 m/sec^2)`=1535.9678 kg