Answer:
94.8 m
Explanation:
The motion of the bike is a uniformly accelerated motion (=constant acceleration), so we can use the following suvat equation:

where:
s is the distance covered
u is the initial velocity
v is the final velocity
t is the time elapsed
For the bike in this problem, we have:
u = 4.3 m/s is the initial velocity
v = 11.5 m/s is the final velocity
t = 12 s is the time
Solving for s, we find the length of the hill:

The energy stored in the chemical bonds are released and the energy causes surrounding molecules to move faster. Chemical energy released as the coal is burned heats water and turns it to steam
S=d/t this is because speed is just the measurement of time and distance
Density is mass over volume: d=m/v
d = 393/50 => d = 7.86 g/ml