Explanation:
1. Force=mass*acceleration
acceleration=force/mass
=100/50
=2m/s^2
2. Gravitational force for downward acceleration= mg-ma=m(g-a) , since a is less than g,
So it will be= 50(9.8-2)
=50(7.8)= 390N
The average power is 
Explanation:
First of all, we calculate the work done to accelerate the car; according to the work-energy theorem, the work done is equal to the change in kinetic energy of the car:
where
:
is the final kinetic energy of the car, with
m = 2000 kg is the mass of the car
v = 60 m/s is the final speed of the car
is the initial kinetic energy of the car, with
u = 30 m/s is initial speed of the car
Soolving:
Now we can find the power required for the acceleration, which is given by

where
t = 9 s is the time elapsed
Solving:

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