You hold a brick at rest in your hand. Are these forces an action-reaction pair? Explain.

Consider the truss in previous problem. Determine the axial forces in members $E H$ and $F H$.

Describe three ways in which you exerted forces earlier today to cause motion.

A proton and an electron are placed in a uniform electric field. Comment on the magnitudes of the forces experienced by both.

What is the symmetry between the laws of Charles Coulomb and Sir Isaac Newton regarding forces?

Solve Prob. earlier , assuming that the magnitude $P$ of the two forces is increased to $120 \mathrm{kN}$.

Model pulleys. Make three drawings. Draw arrows to show forces, and describe the function.

What is the evidence that all neutral atoms and molecules exert attractive forces on each other?

What types of forces, intramolecular or intermolecular,
(c) are overcome when liquid water is vaporized?

When two billiard balls collide, the instantaneous forces between them are very large but act only in an infinitesimal time $\Delta$t, in such a manner that the quantity

$$\int_{\Delta t} F d t$$

remains finite. Such forces are described as impulsive forces, and the integral over $\Delta$t is known as the impulse of the force. Show that if impulsive forces are present Lagrange’s equations may be transformed into

$$\left(\frac{\partial L}{\partial \dot{q}_{j}}\right)_{f}-\left(\frac{\partial L}{\partial \dot{q}_{j}}\right)_{i}=S_{j}$$

where the subscripts i and f refer to the state of the system before and after the impulse, $S_{j}$ is the impulse of the generalized impulsive force corresponding to $q_{j}$, and L is the Lagrangian including all the nonimpulsive forces.

Why did both pro- and antislavery forces believe that victory in Kansas was critical to their cause?

What did Muslim forces hope to accomplish at the Battle of Tours and what actually happened?

Two forces produce the same torque. Does it follow that they have the same magnitude? Explain.

Describe the forces, both attractive and repulsive, that occur as two atoms move closer together.