Answer:
The 1200 kg car.
Explanation:
The 1200 kg car had bo momentum at the initial stage of the journey because it wasn't on motion. But after collision with the 2000 kg car it gained alot of momentum.
Answer:
Energy converted = 
Explanation:
Recall that Power is the rate at which energy is transferred therefore defined by the mathematical formula: 
Since the information on the power of the runner is given, as well as the time the energy conversion takes place, we can then use this equation to find how much energy is been converted. Notice that we just need to change the given time *10 minutes) into the appropriate units (seconds)to get the answer in SI units of energy (Joules). The conversion of 10 minutes into seconds is done by multiplying : 10 minutes * 60 seconds/minute = 600 seconds.
We use this then to find the energy converted by the runner:

Answer: Scientists observe natural events occuring around them. If a hypothesis is not veriffied by the results from the scientific method, scientists may redo the process or create a new hypothesis
Explanation:
The last one is correct (D)
Answer:
speed of current is 5 mile/hr
Explanation:
GIVEN DATA:
speed of motorboat = 15 miles/hr relative with water
let c is speed of current
15-c is speed of boat at upstream
15+c is speed of boat at downstream
we know that
travel time=distance/speed

150+10c+150-10c=1.5(15-c)(15+c)
300=1.5(225-c^2)
300=337.5-1.5c^2
200=225-c^2
c^2=25
c = 5
so speed of current is 5 mile/hr