When people look through a telescope, air currents in the earth’s atmosphere can distort the images they see. in the 1950s, a scientist named h. w. babcock thought of a way to reduce this distortion by using a special device within the telescope. however, this device was not used until the 1990s. which best explains why babcock’s idea took many years to become a reality?

•• al and bert are jogging side-by-side on a trail in the woods at a speed of 0.75 m/s. suddenly al sees the end of the trail 35 m ahead and decides to speed up to reach it. he accelerates at a constant rate of 0.50 m/s2, while bert continues on at a constant speed. (a) how long does it take al to reach the end of the trail? (b) once he reaches the end of the trail, he immediately turns around and heads back along the trail with a constant speed of 0.85 m/s. how long does it take him to meet up with bert? (c) how far are they from the end of the trail when they meet?

Which simple machine is not part of this compound machine? a. lever b. pulley c. inclined plane d. wheel and axle

If a spring has a k value of 100 newtons per meter and it is stretched 0.50 meters, what is the restoring force of the spring?