An echo is heard when sound is reflected off a surface. Which of the following best explains this phenomenon?

A space shuttle is in orbit about the earth at an altitude where the acceleration due to gravity is 8.70 m/s2. What is the shuttle's speed at this altitude? 2.65 * 10 3 m/s 7.45 * 10 3 m/s 7.68 * 10 3 m/s 7.91 * 10 3 m/s

Why is the universe here and why do we exist?

The advantage of a synchronous orbit is that the satellite can: fly over the entire earth transmit over the entire earth receive continuous signals from a ground transmitter all of the above

In the Winter Olympics, an ice skater may lift his partner high above his head. A typical female ice skater weighs 400 N, and the male can usually lift her 1.4 m above the ice.

Why is it important that radioisotopes used in diagnostic tests have short half-lives? 20 A) These radioisotopes have a greater activity so they B) This minimizes the harmful side effects of the radiation.

A change from one form of energy into another is called a. gravitational potential energy. b. work. c. conservation of energy. d. an energy transformation

4. An airplane must achieve a velocity of 71 m/s for takeoff. If the runway is 1000 m long, what must the acceleration be?

As the average kinetic energy of the particles in a gas increases, which of the following occurs?

Power=170 watts time=20 seconds

What is the charge of alpha, beta and gamma rays?