An effect analogous to two-slit interference can occur with sound waves, instead of light. in an open field, two speakers placed 1.30 m apart are powered by a single function generator producing sine waves at 1200-hz frequency. a student walks along a line 12.5 m away and parallel to the line between the speakers. she hears an alternating pattern of loud and quiet, due to constructive and destructive interference. what is : (a) the wavelength of this sound and (b) the distance between the central maximum and the first maximum (loud) position along this line

2.72 m

Explanation:

wavelength of sound λ = velocity / frequency

= 340 / 1200

= .2833 m

Distance of point of  first constructive interference

= λ D / d ( D is distance of the screen and d is distance between source of sound.

Here D = 12.5 m

d = 1.3 m

λ D / d= ( .2833 x 12.5) / 1.3

= 2.72 m

Distance of point of  first constructive interference = 2.72 m

b. lifting dumbbell weight at 20-degree angle from the body after a 45-degree angle

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.