Two trains on opposite tracks leave the same station at the same time. one train travels at an average speed of 80 km/hr and the other travels at an average speed of 70 km/hr. how long after they leave the station will they be 50 km apart?

We can write the law of motion for both trains, calling them train A and train B. Since they both move by uniform motion, so with constant velocity, we can write their position at time t as:

where  and  are the average speeds of the two trains. For the train B, we put a negative sign, since it is going in the opposite direction.

We want to know the time t after which the distance between the two trains is 50 km. In equations, this means finding the time t after which

And solving, we find:

Which means after 20 minutes.

a) cold, dry

explanation:

continental polar masses are cold and dry air masses because the cold air cannot hold much moisture. as they move into warmer air, they can trigger precipitation.

which piece of furniture will have the most inertia and give the furniture movers the most difficulty in moving?  

answer

a 75kg dining table