Answer:
the blue shopping cart.
Explanation:
The blue shopping cart doesnt have to worry about running someone over in the front. The red one does, so it slows down more.
A beam of laser is directed at a reflecting surface put on the moon when the beam of laser is reflected a receiver on the each measure the time since the beam was sent till it was received. Laser is simply light so it has constant velocity in vacuum ~ air (c = 3 x 10^8 m/s)
to find the distance:
t : time measured between launching the beam and receiving it
d : distance
d = ct
