Answer:
![3.3\cdot 10^3\:\mathrm{N}](https://tex.z-dn.net/?f=3.3%5Ccdot%2010%5E3%5C%3A%5Cmathrm%7BN%7D)
Explanation:
Impulse on an object is given by
.
However, it's also given as change in momentum (impulse-momentum theorem).
Therefore, we can set the change in momentum equal to the former formula for impulse:
.
Momentum is given by
. Because the truck's mass is maintained, only it's velocity is changing. Since the truck is being slowed from 26.0 m/s to 18.0 m/s, it's change in velocity is 8.0 m/s. Therefore, it's change in momentum is:
.
Now we plug in our values and solve:
(two significant figures).