Question 1

A bridge is designed so that it does not accelerate or rotate under load. Which two conditions must be satisfied for the bridge to be in static equilibrium?

Accepted Answer

The sum of all forces and the sum of all torques must be zero.

Question 2

A wheel has two equal and opposite forces acting on it, but at different points. What will happen to the wheel?

Accepted Answer

It will rotate because the net torque is not zero.

Question 3

Which statement about the choice of reference point for calculating torque in static equilibrium is correct?

Accepted Answer

The reference point can be chosen arbitrarily for convenience.

Question 4

A uniform bar of length $$L$$ and weight $$W is $$supported at both ends. What is the upward force at each support?

Accepted Answer

$$F_1$$ = $$F_2$$ = \frac{W}{2}$$

Question 5

A painter hangs a paintbrush from a string. If the center of mass of the brush is not directly below the point of suspension, what will happen?

Accepted Answer

The brush will rotate until its center of mass is directly below the suspension point.

Question 6

A ladder leans against a frictionless wall and rests on a floor with friction coefficient $$\mu_s. If a $$person climbs the ladder, what determines how far up the ladder they can go before it slips?

Accepted Answer

The friction at the floor and the position of the center of mass.

Question 7

Which formula correctly expresses Young's modulus $$Y$$ for a material under tensile stress?

Accepted Answer

$$Y = \frac{F/A}{\Delta l / l_0$}$$

Question 8

A steel cable of cross-sectional area $$A = 0.002 \ \mathrm{m}^2$$ and length $$l_0 = 3.0$$ \ \mathrm{m}$$ stretches by $$\Delta l = 0.004 \ \mathrm{m}$$ under a load of F = 5500$$ \ \mathrm{N}$$. What is the strain in the cable?

Accepted Answer

$$\mathrm{strain} = \frac{\Delta l}{l_0$} = \frac{0.004}{3.0} = 0.00133$$

Question 9

Which of the following best describes the base of support for an object at rest?

Accepted Answer

The area bounded by whatever is touching the floor.

Question 10

A block is resting on an inclined plane. At what point will the block tip over?

Accepted Answer

When the center of mass is outside the base of support.

Question 11

Which equation represents the condition for rotational equilibrium for a rigid body?

Accepted Answer

$$\sum 	au = 0$$

Question 12

A uniform rod of length $$d is $$used as a lever. If a force $$F is $$applied at one end and a load $$L at $$the other, where should the support point $$P be $$placed to balance the lever?

Accepted Answer

$$x = \frac{L + W/2}{R + W/2} d$$

Question 13

Which of the following is NOT a type of elastic modulus?

Accepted Answer

Thermal modulus

Question 14

A material is stretched beyond its elastic limit. What behavior does it exhibit?

Accepted Answer

It undergoes plastic deformation and may eventually fracture.

Question 15

Which formula correctly expresses the bulk modulus $$B$$?

Accepted Answer

$$B = -\frac{\Delta p}{\Delta V / V_0$}$$

Question 16

A steel beam is under both tensile and compressive stress. Where is the tensile stress greatest?

Accepted Answer

At the bottom of the beam.

Question 17

Which equation gives the shear modulus $$S$$ for a material?

Accepted Answer

$$S = \frac{F/A}{x/h}$$

Question 18

A ladder is placed at an angle $$	heta to $$the floor. What is the minimum angle $$	heta_{min} at $$which the ladder will not slip if the coefficient of static friction is $$\mu_s$$?

Accepted Answer

$$	heta_{min} = \arctan(1/\mu_s)$$

Question 19

Which of the following statements about Hooke's Law is correct?

Accepted Answer

Hooke's Law applies only up to the elastic limit of a material.

Chapter 11: Equilibrium and Elasticity – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards