A car moving at 70 km/hr has a mass of 1700 kg. What force is necessary to decelerate it at a rate of 40 cm/s/s?

1 Answer
Apr 19, 2018

F= -680 N

Explanation:

"Force" = "mass"*"acceleration"
Ref: Newton's 2nd Law commonly written F= m*a

The acceleration is -40 cm/s/s. (I added the negative sign to the given deceleration rate because the acceleration is in the direction opposite the velocity.) That data needs to be converted to have units of m/s^2.

-40 "cm/s/s" = -40 cancel("cm")/s^2 * (1 m)/(100 cancel(cm)) = -0.4 m/s^2

Plugging our data into F= m*a,

F= 1700 kg*(-0.4 m/s^2) = -680 kg*m/s^2 = -680 N

Minus sign indicate that force is in opposite direction.

I hope this helps.