How did people measure speed before speedometers and radar guns were invented

Now suppose the crate is lifted so rapidly that air resistance was significant during the raising. How much work was done by the lifting force as the box was raised 1.5 m?

A triangular plate made of homogeneous material has a constant thickness that is very small. if it is folded over as shown, determine the location z¯ of the plate's center of gravity g.

Explain why sound energy is not a type of potential energy

A mixture is/is not a chemical combining of substances

How does magnet polarity affect the current flowing in a loop of wire?

According to the concept of length contraction, what happens to the length of an object as it approaches the speed of light and then slows down, eventually coming to a stop? It is always observed as contracting.

If you could chooses between to nearly identical products the one that is free and the other you have to pay for which would you choose why

A bicyclist bikes the 56 mi to a city averaging a certain speed. The return trip is made at a speed that is 6 mph slower. Total time for the round trip is 11 hr. Find the bicyclist's average speed on each part of the trip.

You have two pendulums with cords that are exactly the same length. one is on earth (with an acceleration due to gravity of 9.81 meters/second2) and the other one is on the moon (with an acceleration due to gravity of 1.63 meters/second2).

A light-rail train going from one station to the next on a straight section of track accelerates from rest at 1.1 m/s2 for 20 s. It then proceeds at constant speed for 1100 m before slowing down at 2.2 m/s2 until it stops at the station.