A force of 49 Newtons is applied to a rock, which causes it to be lifted 2 meters in 5 seconds. How much power is exerted during this time? Select one:
9.8 W
19.6 W
56.4 W
98 W

 19.6 watts

Explanation:

power = (change in work)/(change in time)

p = w/t

work = force*displacement

w = f*d

So we can say:

p = (f*d)/t

We know the following

Leading to...

p = (f*d)/t

p = (49*2)/5

p = 98/5

p = 19.6 watts

Side note: 1 watt is equal to 1 joule per second

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.