Distance between the motion sensor and the cart, if the reflected ech was recorded after 0.005s?

Question

The ultrasonic motion sensor sends pulses of ultrasound toward a cart on the low-friction track and determines the distance by the time an echo takes to return. The temperature in the lab is equal to 20 degrees C.

b. The velocity of sound in air is a function of temperature and changes by 0.6 m/s for every degree Celsius (°C) of the temperature change. The velocity of sound is proportional to the temperature. What would be the apparent distance between the motion sensor and the cart, if the temperature in the lab increases by DT = 11.8 °C?

thanks remo aviron!! i didn't divide by 2 apparently...

Answer 1

V = Speed of Sound at 20 deg C = 343.2 m/sec . . . ref: http://en.wikipedia.org/wiki/Speed_of_sound

Time = 0.005 sec

Distance traveled = 2* Distance to Cart

V=d/t
d=v*t
Distance Traveled = 2* Distance to Cart = V*T

Distance to Cart = V*T/2

Plug in the numbers.

You should get between .85 and .90 meters.