An observer on the ground sees an eagle flying towards thep east at 15m/s chasing a hummingbird flying at 5 m/s. He approximates that the mass of the eagle is 4 times that of the hummingbird. If the eagle catches the hummingbird and continues to fly with the same thrust from its wings, what speed with the observer see them moving at?

The small gear has 10 teeth and the big gear has 50 teeth. When the small gear rolls around the big gear, how many times will the arrow return to its initial orientation (pointing upward)?

A ballet dancer of mass 80 kg and a wingspan of 80cm is executing a spin. She then folds her arms and brings them to within 20 cm from the central axis of her body. If she was initially making 3 rotations per second, how many does she make now?

"The World Health Organisation has recorded 184 human cases of the H5N1 strain of bird flu, all of them caused by contact with infected birds. That 103 of these have resulted in death indicates how dangerous this virus is, and no vaccine has yet been developed. For there to be a worldwide epidemic of H5N1 amongst humans, it would have to be possible for the virus to be passed easily from one person to another. Unlike normal influenza, H5N1 can only bind to receptors deep in the lungs. As a result, it cannot multiply in the upper respiratory system and thereby be transmitted by sneezing and coughing. So it cannot be transmitted easily between people. Influenza viruses can mutate, and thus possibly change the way in which they infect victims." Which of the following can be drawn as a conclusion from the passage above?

Why is the pupil of the human eye black?

Why does the burning of a tire yield black smoke while burning stoves in homes rarely produce smoke?

When driving a car around a corner, why do we feel as if we are thrown away from the corner?