I think it will reduce in speed because friction drags it to the opposite direction and it were the girls mass that was overcoming friction but i think it is newtons 2nd law of motion
Given: Universal Gravitational constant = G = 6.67 x 10⁻¹¹ N m²/Kg²
Mass₁ = 70 Kg; Mass₂ = 70 Kg Radius r = 1.5 m; Force F = ?
Formula: F = Gm₁m₂/r²
F = (6.67 x 10⁻¹¹ N m²/Kg²)(70 Kg)(70 Kg)/(1.5 m)²
F = 1.45 X 10⁻⁷ N
"2 km/hr/s" means that in each second, its engines can increase its speed by 2 km/hr.
If it keeps doing that for 30 seconds, its speed has increased by 60 km/hr.
On top of the initial speed of 20 km/hr, that's 80 km/hr at the end of the 30 seconds.
This whole discussion is of <em>speed</em>, not velocity. Surely, in high school physics,
you've learned the difference by now. There's no information in the question that
says anything about the train's <em>direction</em>, and it was wrong to mention velocity in
the question. This whole thing could have been taking place on a curved section
of track. If that were the case, it would have taken a team of ace engineers, cranking
their Curtas, to describe what was happening to the velocity. Better to just stick with
speed.
