At maximum speed an airplane travels 1720 miles against the wind in 5 hours. flying with the wind, the plane can travel the same distance in 4 hours. let x be the maximum speed of the plane and y be the speed of the wind. what is the speed of the plane with no wind?

387 miles / hour

Explanation:

X be the maximum speed of plane and Y be the speed of wind.

Speed is the ratio of distance traveled to the time taken by the body.

When the plane travels against the wind, the speed of the plane is X - Y and when the plane is moving with the wind the speed is X + Y.

According to the formula

X - Y = 344 ....(1)

And

X - Y = 430 ......(2)

Adding both the equations,

2X = 774

X = 387 miles/hour

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.

you'd use the equation that establishes a relationship between  energy  and  wavelength, which looks like this

e=h⋅cλ, where

λ  - the wavelength of the photon; c  - the speed of light, usually given as  3⋅108m/s; h  -  planck's constant, equal to  6.626⋅10−34j s

plug the value you were given for the energy of the photon in the above equation to get the wavelength

e=h⋅cλ⇒λ=h⋅ce

λ=6.626⋅10−34js⋅3⋅108ms−1.257⋅10−24j=1.581⋅10−1m