What upward gravitational force does a 5600 kilogram elephant exert on Earth?

You're a safety engineer for a bridge spanning the U.S.-Canadian border. U.S. specifications permit a maximum load of 10 tons. What load limit should you specify on the Canadian side, where "weight" is given in kilograms?

Kinesin is a "motor protein" responsible for moving materials B10 within living cells. If it exerts a 6.0 pN force, what acceleration will it give a molecular complex with mass $3.0 \times 10^{-18} \mathrm{~kg}$ ?

Does Venus exhibit retrograde motion? Explain.

True or false? The planets all orbit around the Sun in the same direction because the planets gravitationally tug on each other, causing them to move in the same direction.

True or false? The outer planets orbit the Sun with a smaller physical speed km/s than the inner planets.

True or false? Copernicus's greatest contribution to astronomy was that he put forth the notion that retrograde motion can be explained by having the planets move along epicycles.

True or false? The orbital period and distance of a planet from the Sun can be used, with Newton's version of Kepler's third law, to estimate the mass of the Sun.

True or false? Although the values of the constants may differ, Newton showed that Kepler's laws apply equally well to the moons orbiting Jupiter, if "moon" and "Jupiter" are substituted for the words "planet" and "Sun," respectively.

True or false? In Ptolemy's geocentric theory of the Solar System, Venus could not go through the complete set of phases observed by Galileo.

True or false? An external force is needed to keep an object in motion at a constant speed and a constant direction.

Far in space, where gravity is negligible, a $425 \mathrm{~kg}$ rocket traveling at $75.0 \mathrm{~m} / \mathrm{s}$ in the positive $x$-direction fires its engines. as we discussed earlier shows the thrust force as a function of time. The mass lost by the rocket during these $30.0 \mathrm{~s}$ is negligible.
a. What impulse does the engine impart to the rocket?
b. At what time does the rocket reach its maximum speed? What is the maximum speed?

If you were standing on a spinning turntable holding barbells close to your chest and you extended your arms, how would your spin rate be affected? Why?

We often use the term "inertia" to describe human sluggishness. How is this usage related to the meaning of "inertia" in physics?