1. An automatic focus camera is able to focus on objects by use of an ultrasonic sound wave. The camera sends out sound waves that reflect off distant objects and return to
the camera. A sensor detects the time it takes for the waves to return and then
determines the distance an object is from the camera. If a sound wave (speed = 345
m/s) returns to the camera 0.115 seconds after leaving he camera, how far away is the
object?

19.84 m

Explanation:

The following data were obtained from the question:

Speed of sound (v) = 345 m/s

Time (t) = 0.115 s

Distance (x) =?

The distance of the object away can be obtained as follow:

v = 2x / t

345 = 2x / 0.115

Cross multiply

345 × 0.115 = 2x

39.675 = 2x

Divide both side by 2

x = 39.675 / 2

x = 19.84 m

Thus, the object is 19.84 m away from the camera.

568.98

explanation:

its math

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s