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.

answer: 802.3 kilo joules of energy represents 191.75 kilo calorie of energy.

explanation:

energy released during combustion of one mole methane = 802.3 kilo joules

if 1 kilo joule = 0.239006   kilo calorie

then ,802.3 kilo joule will be = 802.30.239006 kilo calorie

802.3 kilo joule = 191.75 kilo calorie

hence, the energy in kilo calorie is 191.75 kilo calorie.