Take into account that the force can be written as follow:

where,
Δp: change in momentum = 17 kg.m/s
Δt: time interval at which the force change the momentum = 5 s
Replace the previous values of the parameters into the formula for F, and simplify:
![F=\frac{17\operatorname{kg}(m)/(s)}{5s}=3.4\operatorname{kg}(m)/(s^2)=3.4N]()
Then, a force of 3.4N would be needed to change the momentum of an object 17 kgm/s in 5s.