Let's use Newton's 2nd law of motion:
Force = (mass) x (acceleration)
Force = (68 kg) x (1.2 m/s²) = 81.6 newtons .
Answer:
The thrown rock strike 2.42 seconds earlier.
Explanation:
This is an uniformly accelerated motion problem, so in order to find the arrival time we will use the following formula:

So now we have an equation and unkown value.
for the thrown rock

for the dropped rock

solving both equation with the quadratic formula:

we have:
the thrown rock arrives on t=5.4 sec
the dropped rock arrives on t=7.82 sec
so the thrown rock arrives 2.42 seconds earlier (7.82-5.4=2.42)
Answer:
Global dependence on fossil fuels has associated social costs.
Explanation:
Increased dependence on fossil fuels reduces their availability. When the demand is high and the availability is low, the price rises. Not every nation would then be able to afford buying fossil fuels at such high costs.
Developing and underdeveloped countries would then be left behind and only the wealthy nations would be able to afford fossil fuel purchase. This would be the immediate impact of global dependence on fossil fuels.
Fossil fuels are mainly coal, petroleum and natural gas. Since fossil fuels are non-renewable in nature over exploitation may lead to fossil fuels getting exhausted.