Answer:
168 seconds (2 min 48 s)
Explanation:
Find the heat absorbed by the water.
q = mCΔT
q = (1 kg) (4200 J/kg/K) (70°C − 40°C)
q = 126,000 J
Power is energy per time.
P = q / t
750 W = 126,000 J / t
t = 168 s
It takes 168 seconds (2 min 48 s).
Let north as positive
Fnet=10n-5n
=5n north
The answers is 30 miles per hour, the driver is speeding the car up, section-H, 12 minutes, section-D, and 65 miles per hour.
The force exerted on the box is 56 N
Explanation:
The work done by a force on an object is given by

where
F is the magnitude of the force
d is the displacement of the object
is the angle between the direction of the force and of the displacement
For the box in this problem, we have:
W = 2240 J is the work done
d = 40 m is the displacement of the box
Assuming that the force is parallel to the displacement, 
Solving the equation for F, we find the force exerted on the box:

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