Question 1

Which of the following statements best describes the condition for force equilibrium in a static system?

Accepted Answer

The sum of all external forces acting on the object is zero: $$\sum \vec{F} = \vec{0}$$

Question 2

A car is at rest on a flat surface. Which forces must be included in its free-body diagram?

Accepted Answer

Body force (weight) and surface forces (normal reactions from the ground)

Question 3

Which of the following is an example of a surface force?

Accepted Answer

The normal force exerted by the ground on a parked car

Question 4

In a system of concurrent forces, what is true about the lines of action of all forces?

Accepted Answer

They all intersect at a single point

Question 5

A block of weight $$W is $$suspended by two cables, AB and AC, at angles $$\$$theta_1$$ and $$\$$theta_2$$ from the vertical. Which equation expresses the equilibrium of forces in the vertical direction?

Accepted Answer

$$T_{AB} \cos \$$theta_1$$ + T_{AC} \cos \$$theta_2$$ = W$$

Question 6

Which of the following best describes the difference between internal and external forces?

Accepted Answer

Internal forces are exerted by one part of an object on another part of the same object; external forces are exerted by a different object.

Question 7

A stationary block is suspended by a cable. If the block has mass $$m$$, what is the tension $$T in $$the cable?

Accepted Answer

$$T = mg$$

Question 8

When drawing a free-body diagram (FBD), which of the following steps is NOT recommended?

Accepted Answer

Include irrelevant details such as decorative features

Question 9

A person pushes horizontally on a wall. Which force acts parallel to the surface of contact?

Accepted Answer

Friction force

Question 10

For a body in equilibrium in three dimensions, which set of equations must be satisfied?

Accepted Answer

$$\sum F_x = 0$$, $$\sum F_y = 0$$, $$\sum F_z = 0$$

Question 11

A motorcycle is suspended by three cables at point A. If the system is in equilibrium, what must be true about the vector sum of the tensions in the cables and the weight of the motorcycle?

Accepted Answer

$$\vec{T}_{AB} + \vec{T}_{AC} + \vec{T}_{AD} + \vec{W} = \vec{0}$$

Question 12

Which of the following is a correct statement about the line of action of a force?

Accepted Answer

It is the straight line along which the force acts

Question 13

A block is suspended by two cables at different angles. If the block is stationary, which principle is being applied?

Accepted Answer

Force equilibrium: the sum of all forces is zero

Question 14

Which of the following is NOT a body force?

Accepted Answer

Normal force exerted by the ground

Question 15

A block of mass $$m is $$suspended by a cable and remains stationary. If the cable is replaced by a spring with spring constant $$k$$, what is the extension $$x of $$the spring at equilibrium?

Accepted Answer

$$x = \frac{mg}{k}$$

Question 16

When analyzing contact forces between two curved surfaces, which statement is correct?

Accepted Answer

The normal force is perpendicular to the plane tangent to the surfaces at the point of contact

Question 17

A block is suspended by two cables, each making an angle $$	heta$$ with the vertical. If the block has weight $$W$$, what is the tension $$T in $$each cable?

Accepted Answer

$$T = \frac{W}{2 \cos 	heta}$$

Question 18

Which of the following is a correct application of the equations of equilibrium in two dimensions?

Accepted Answer

$$\sum F_x = 0$$ and $$\sum F_y = 0$$

Question 19

A block is suspended by a cable over a pulley. If the pulley is ideal (frictionless and massless), what is true about the tension in the cable on both sides of the pulley?

Accepted Answer

The tension is the same on both sides of the pulley

Statics: Forces and Equilibrium (Chapter 3 Study Notes)

Study Guide - Practice Questions

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