Answer:
The answer is
<h2>28 kg</h2>
Explanation:
The mass of an object given it's momentum and velocity / speed can be found by using the formula

where
m is the mass
p is the momentum
v is the speed or velocity
From the question
p = 280 kg/ms
v = 10 m/s
The mass of the object is

We have the final answer as
<h3>28 kg</h3>
Hope this helps you
To solve this problem we will apply the concepts related to volume, as a function of length and area, as of mass and density. Later we will take the same concept of resistance and resistivity, equal to the length per unit area. Once obtained from the known constants it will be possible to obtain the area by matching the two equations:
Mass of copper wire
Density
Resistively of copper 
Resistance (R) = 0.390\Omega
Volume is defined as,

(1)
We know that,


(2)
Multiplying equation we have




Therefore the length of the wire is 1.68m
-- The train starts at 23 m/s and slows down by 0.25 m/s every second.
So it'll take (23/0.25) = 92 seconds to stop.
-- Its average speed during that time will be (1/2)(23+0) = 11.5 m/s
-- Moving at an average speed of 11.5 m/s for 92 sec, the train will cover
(11.5 m/s) x (92 sec) = <em>1,058 meters</em> .