Atruck is moving at the rate of 40 km/hr. how far does it move when it stops after 5 seconds?

First of all, this is the chemistry section, while your question is a physics question. Anyway I'll tell you how to solve it.

First we need to find the rate that the truck moves in a second.

1km = 1000m
40km = 40000m
40000m/hr
1 hour = 60 minutes
40000m/hr ÷ 60 = 666.66(repeating)/minute
1 minute = 60 seconds
666.66m/min ÷ 60 = 11.11(rep)m/s

Next we simply multiply the speed of the truck by the number of seconds it travels.

11.11 × 5 = 55.55
Make sure to round it unless you indicate the repeating decimal.
The truck moved 55.56m in 5 seconds.