Chapter 3: Dynamics: Force and Newton's Laws of Motion - Review Questions

What is the definition of force as described in the text?

a) A scalar quantity that causes motion

b) A vector quantity that represents a push or pull

c) A measure of mass

d) A unit of energy

b) A vector quantity that represents a push or pull

Which method is used to add forces as vectors?

a) Head-to-tail method

b) Algebraic addition

c) Subtraction

d) Multiplication

a) Head-to-tail method

What is a free-body diagram used for?

a) To illustrate internal forces within a body

b) To show all external forces acting on a body

c) To measure the mass of a body

d) To calculate the velocity of a body

b) To show all external forces acting on a body

What is a restoring force?

a) A force that opposes motion

b) A force that returns an object to its original shape

c) A force that accelerates an object

d) A force that acts only on liquids

b) A force that returns an object to its original shape

Force is a ___ quantity that has both magnitude and direction.

vector

What is the purpose of using a standard unit of force?

A standard unit of force allows for the consistent measurement and comparison of forces, similar to how standard units of distance are used.

What does Newton's First Law of Motion state?

a) A body at rest remains at rest unless acted on by a net external force.

b) A body in motion remains in motion unless acted on by a net external force.

c) A body at rest remains at rest, or if in motion, remains in motion at a constant velocity unless acted on by a net external force.

d) A body in motion will eventually come to rest due to internal forces.

c) A body at rest remains at rest, or if in motion, remains in motion at a constant velocity unless acted on by a net external force.

What is the cause of an object slowing down when sliding on a surface?

a) Gravity

b) Friction

c) Inertia

d) Mass

b) Friction

Which of the following best describes inertia?

a) The tendency of an object to change its velocity.

b) The tendency of an object to remain at rest or in uniform motion unless acted upon by an external force.

c) The force required to move an object.

d) The weight of an object.

b) The tendency of an object to remain at rest or in uniform motion unless acted upon by an external force.

How is mass related to inertia?

a) Mass is unrelated to inertia.

b) Mass is a measure of inertia.

c) Mass is the same as inertia.

d) Mass is the force that causes inertia.

b) Mass is a measure of inertia.

What happens to an object on a frictionless surface according to Newton's First Law?

a) It comes to a stop due to internal forces.

b) It continues to move at a constant velocity.

c) It accelerates indefinitely.

d) It moves in a circular path.

b) It continues to move at a constant velocity.

The property of a body to remain at rest or to remain in motion with constant velocity is called ___.

inertia

A net external force is required to change the ___ of an object.

velocity

Explain how friction affects the motion of an object according to Newton's First Law.

Friction is an external force that opposes the motion of an object, causing it to slow down and eventually stop if no other forces act on it.

Why is mass considered a measure of inertia?

Mass is considered a measure of inertia because it quantifies the amount of resistance an object has to changes in its state of motion.

What is the SI unit of force?

a) Newton

b) Pound

c) Kilogram

d) Meter per second squared

a) Newton

According to Newton's second law, what happens to acceleration if the net external force is doubled while the mass remains constant?

a) Acceleration doubles

b) Acceleration halves

c) Acceleration remains the same

d) Acceleration quadruples

a) Acceleration doubles

Which of the following best describes weight?

a) A measure of mass

b) A measure of gravitational force

c) A measure of inertia

d) A measure of velocity

b) A measure of gravitational force

What is the relationship between mass and acceleration according to Newton's second law?

a) Directly proportional

b) Inversely proportional

c) Unrelated

d) Exponentially proportional

b) Inversely proportional

What does a bathroom scale measure when you stand on it?

a) Your mass

b) Your weight

c) Your inertia

d) Your velocity

b) Your weight

The net external force is the vector sum of all ___ forces acting on a system.

external

Weight is the gravitational force acting on an object and is calculated as the product of mass and the acceleration due to ___.

gravity

Define net force and explain its significance in Newton's second law of motion.

Net force is the vector sum of all external forces acting on a system. It is significant in Newton's second law because it determines the acceleration of the system, as acceleration is directly proportional to the net force.

How does Newton's second law of motion relate force, mass, and acceleration?

Newton's second law states that the acceleration of a system is directly proportional to the net external force acting on it and inversely proportional to its mass. This is expressed as F = ma.

Explain the difference between mass and weight.

Mass is the amount of matter in an object and is constant regardless of location. Weight is the gravitational force acting on an object and varies with the strength of the gravitational field.

What does Newton's third law of motion state?

a) For every action, there is an equal and opposite reaction.

b) An object in motion stays in motion unless acted upon by an external force.

c) The acceleration of an object is directly proportional to the net force acting on it.

d) The force of gravity acts between all masses.

a) For every action, there is an equal and opposite reaction.

In the context of Newton's third law, why do action and reaction forces not cancel each other out?

a) They act on different systems.

b) They are not equal in magnitude.

c) They are not opposite in direction.

d) They occur at different times.

a) They act on different systems.

Which of the following is an example of Newton's third law in action?

a) A car accelerating forward due to the ground pushing on its wheels.

b) A book resting on a table.

c) A satellite orbiting Earth.

d) A ball rolling down a hill.

a) A car accelerating forward due to the ground pushing on its wheels.

According to Newton's third law, forces always occur in ___.

pairs

Explain why a swimmer moves forward when pushing against the pool wall.

A swimmer moves forward because when they push against the pool wall, the wall exerts an equal and opposite force back on the swimmer, propelling them forward.

Why is it important to define a system when analyzing forces?

Defining a system is important because it helps identify which forces are internal and which are external, allowing for accurate application of Newton's laws to analyze motion.

What is the normal force?

a) A force parallel to the surface

b) A force perpendicular to the surface

c) A force along the length of a rope

d) A force due to friction

b) A force perpendicular to the surface

How does tension in a rope behave?

a) It can push and pull

b) It only pulls

c) It only pushes

d) It neither pushes nor pulls

b) It only pulls

What happens to the tension in a rope if the angle θ approaches zero?

a) Tension becomes zero

b) Tension becomes infinite

c) Tension remains constant

d) Tension decreases slightly

b) Tension becomes infinite

What is the effect of friction on an incline?

a) It increases acceleration

b) It decreases acceleration

c) It has no effect on acceleration

d) It reverses the direction of motion

b) It decreases acceleration

What is a fictitious force?

a) A force with a physical origin

b) A force due to an accelerating frame of reference

c) A force that acts only on Earth

d) A force that is always perpendicular to motion

b) A force due to an accelerating frame of reference

The normal force is a force that acts ___ to the surface of contact.

perpendicular

Explain how the normal force acts on an object resting on an incline.

The normal force acts perpendicular to the surface of the incline, supporting the object against gravity.

Describe the role of tension in a rope when supporting a mass.

Tension in a rope acts to balance the weight of the mass, pulling upward along the rope's length.

What is the significance of resolving forces into components on an incline?

Resolving forces into components allows us to analyze the forces acting parallel and perpendicular to the incline, simplifying the problem.

What is the first step in the problem-solving strategy for Newton's laws of motion?

a) Identify the physical principles involved and draw a sketch

b) Apply Newton's second law

c) Check the solution for reasonableness

d) Write net force equations

a) Identify the physical principles involved and draw a sketch

What does a free-body diagram represent?

a) All forces, acceleration, and velocity

b) Only external forces

c) Only internal forces

d) All forces and acceleration

b) Only external forces

A diagram showing the system of interest and all of the external forces is called a ___.

free-body diagram

How can you check if your solution to a physics problem is reasonable?

You can check if your solution is reasonable by considering if the result makes intuitive sense and by verifying that the units are consistent with the quantity being solved for.

What is the drag force on the barge if the net applied force is 4.5×10^5 N and the barge's mass is 5.0×10^6 kg with an acceleration of 7.5×10^-2 m/s^2?

a) 7.5×10^4 N

b) 4.5×10^5 N

c) 3.0×10^5 N

d) 1.5×10^5 N

a) 7.5×10^4 N

In the example of the traffic light suspended by two wires, why is T2 greater than T1?

a) Because T2 is more vertical than T1

b) Because T1 is more vertical than T2

c) Because both tensions are equal

d) Because T2 is less vertical than T1

a) Because T2 is more vertical than T1

What does a bathroom scale read when an elevator moves upward at a constant speed?

a) More than the person's weight

b) Less than the person's weight

c) Equal to the person's weight

d) Zero

c) Equal to the person's weight

What is the average force exerted by a soccer player to reach a velocity of 8.00 m/s in 2.50 s if his mass is 70.0 kg?

a) 224 N

b) 280 N

c) 196 N

d) 350 N

a) 224 N

The drag force is a type of ___ force exerted by fluids such as air or water.

frictional

How do you calculate the drag force on an object moving through a fluid?

The drag force is calculated using the equation FD = Fapp - ma, where Fapp is the net applied force and ma is the product of mass and acceleration.

Explain why the tensions in the wires supporting a traffic light are not equal when the angles are different.

The tensions are not equal because the angles are different, causing the vertical and horizontal components of the forces to differ, requiring different tensions to balance the forces.

What happens to the reading on a bathroom scale when an elevator accelerates downward?

When an elevator accelerates downward, the scale reads less than the person's weight because the net force is reduced by the downward acceleration.

Which of the following forces is responsible for the stability of atomic nuclei?

a) Gravitational Force

b) Electromagnetic Force

c) Weak Nuclear Force

d) Strong Nuclear Force

d) Strong Nuclear Force

What is the carrier particle for the electromagnetic force?

a) Graviton

b) Photon

c) Gluon

d) W and Z Bosons

b) Photon

Which force is considered the weakest among the four basic forces?

a) Gravitational Force

b) Electromagnetic Force

c) Weak Nuclear Force

d) Strong Nuclear Force

a) Gravitational Force

What is the concept used to explain how forces act at a distance?

a) Force Fields

b) Quantum Tunneling

c) Wave-Particle Duality

d) String Theory

a) Force Fields

Which of the following forces can be both attractive and repulsive?

a) Gravitational Force

b) Electromagnetic Force

c) Weak Nuclear Force

d) Strong Nuclear Force

b) Electromagnetic Force

The four basic forces are gravitational, electromagnetic, weak nuclear, and ___.

strong nuclear

Explain the significance of the unification of forces in physics.

The unification of forces in physics aims to show that the four basic forces are different manifestations of a single force. This concept simplifies our understanding of the universe by revealing underlying connections between forces, such as the electroweak force, which unifies the electromagnetic and weak nuclear forces under extreme conditions.

What role do gravitational waves play in our understanding of the universe?

Gravitational waves provide evidence for the predictions of general relativity and offer insights into cosmic events like black hole mergers. They help us understand the dynamics of massive objects and the nature of space-time.