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

Answer:

#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.