#10 #20 #24 #28 #44 10. About how long is a football field in meters?
We know that a football field's length is 100 yards. Since a meter is just a little longer than a yard, a football field is roughly 100 meters in length. (Actually it is about 91 meters long.)
20. An ancient marathoner covered the first 20 miles of a race in 4 hours. Can you determine how fast he was running when he passed the 10-mile marker?
No. While we know that the average speed of the runner was 5 miles/hour, he could have been going either faster or slower than that as he passed the 10-mile marker.
24. If you are told that a car is traveling 65 mph east, are you being given the car's speed or its velocity?
Velocity is defined as speed with direction, here 65 mph to the east. Thus, we are given the car's velocity.
28. Which of the following (if any) could not be considered an "accelerator" in an automobile - gas pedal, brake pedal, or steering wheel?
Recall that the definition of acceleration is the change in velocity divided by the change in time. Since velocity is speed in a particular direction, a non-zero acceleration occurs when there is a change in speed, velocity direction, or both. With that definition in mind, consider each item in the list.
Gas pedal: increases speed.
Brake pedal: decreases speed.
Steering wheel: changes the direction of the velocity.
We conclude that they are all accelerators.
44. A penny and a feather are placed inside a long cylinder and the air is pumped out. The cylinder is inverted. Which hits the bottom first - the penny or the feather?
They both hit the ground at the same time.