3B2 Fundamentals of Motion

Question 1

What is motion in physics?

Answer 1

Refers to the change in position of an object over time.

Question 2

How is motion usually described?

Answer 2

Using terms like displacement, distance, velocity, speed, acceleration, and time.

Question 3

Why is motion usually measured in relation to something?

Answer 3

To establish a frame of reference.

e.g. Earth’s surface

Question 4

What are the four types of motion?

Answer 4

• Linear
• Projectile
• Circular
• Simple harmonic motion

Question 5

What is linear motion?

Answer 5

The movement in a straight line, also called 1-D motion.

Question 6

Give an example of linear motion.

Answer 6

A car driving on a perfectly straight road.

Question 7

What is projectile motion?

Answer 7

Involves two dimensions and includes objects moving in an up-and-down dimension and a forwards-and-back dimension.

Question 8

How is projectile motion graphed differently from linear motion?

Answer 8

It requires separate graphs for displacement, velocity, and acceleration along both the x-axis and y-axis.

Question 9

What is circular motion?

Answer 9

Involves movement along a circular path, like a ball on a string or a satellite orbiting Earth.

Question 10

Why is circular motion considered accelerated motion?

Answer 10

Because the direction of the object’s velocity is constantly changing.

Question 11

What is simple harmonic motion?

Answer 11

Periodic motion where the restoring force is directly proportional to the displacement from an equilibrium position.

Question 12

Give an example of simple harmonic motion.

Answer 12

• Pendulums
• Masses on springs

Question 13

What type of graphs describe simple harmonic motion?

Answer 13

Includes the use of displacement, velocity, and acceleration graphs.

When you plot them, they all turn out to be sine curves.

Question 14

What key concept differentiates circular motion from other forms of motion?

Answer 14

In circular motion, the object’s speed is constant, but its velocity, including direction, changes.

Question 15

What is displacement in the context of motion?

Answer 15

The change in position of an object from its initial point, measured in a specific direction.

Question 16

What is the difference between velocity and speed?

Answer 16

• Velocity includes both the speed and direction of an object’s movement.
• Speed only measures how fast the object is moving.

Question 17

What does a velocity-time graph show?

Answer 17

It illustrates how an object’s velocity changes over time.

Question 18

In which section of the velocity-time graph (in the diagram) is the car travelling at constant speed?

Answer 18

Section B

The line is flat, meaning the car’s speed did not change for 10 seconds – meaning it was moving at a constant speed.

Question 19

How is acceleration defined in physics?

Answer 19

The rate at which an object’s velocity changes over time.

Question 20

Why are sine curves used to describe simple harmonic motion?

Answer 20

They mathematically describe the periodic oscillations of simple harmonic motion.

Question 21

What is the relationship between displacement and distance?

Answer 21

• Displacement is the straight-line distance from start to end in a specified direction.
• Distance is the total path length traveled (regardless of direction).

Question 22

How do you define the equilibrium position in simple harmonic motion?

Answer 22

It is when the net force on the object is zero, and it is the central point around which the object oscillates.

Question 23

What is the significance of the acceleration-time graph in projectile motion?

Answer 23

It shows constant acceleration due to gravity (typically -9.8 m/s²), affecting the object in the y-direction.

Question 24

Define:

translational equilibrium

Answer 24

Occurs when the net force acting on an object is zero, resulting in no linear acceleration and the object either remaining at rest or moving at a constant velocity.

Question 25

Define rotational equilibrium and give an example.

Answer 25

It occurs when the net torque acting on an object is zero, resulting in no angular acceleration and the object either remaining at rest or rotating at a constant angular velocity.

The diagram shows a balanced beam in rotational equilibrium has equal counterclockwise and clockwise torques.

Question 26

What is Newton’s first law of motion?

Answer 26

It states that an object at rest will remain at rest, and an object in motion will remain in motion unless acted upon by an external force.

Question 27

Define:

inertia

Answer 27

It’s the resistance of an object to changes in its state of motion and is proportional to its mass.

Diagram: On the left, the bus is moving with uniform motion in a straight line and the passenger has the same motion. On the right, when the bus stops, the part of the body (lower part) in contact with bus stops, but due to inertia the upper part continues to move forward and thus he moves forward.

Question 28

What did Galileo contribute to Newton’s first law?

Answer 28

He developed the concept of inertia, explaining that objects resist changes in motion and eventually stop due to frictional force.

Question 29

How did Descartes’ view on motion differ from Newton’s?

Answer 29

Descartes believed only direct collisions influence motion, while Newton included other forces like friction.

Question 30

How does Newton’s first law apply to space?

Answer 30

In space, an object will continue moving at a constant velocity unless acted upon by an unbalanced force, as space is nearly void of matter and gravity.

Question 31

How does Newton’s first law explain dizziness?

Answer 31

That it occurs because the fluid in the ear continues moving after the body stops spinning, demonstrating inertia.

Question 32

What happens to liquids during sudden stops according to Newton’s first law?

Answer 32

Liquids resist changes in motion, so when a vehicle stops suddenly, the liquid continues moving forward, causing spills.

Question 33

How is Newton’s first law demonstrated with a sliding book?

Answer 33

A sliding book eventually stops due to friction, illustrating that it continues in motion until an unbalanced force (friction) acts on it.

Question 34

What misconception did Newton’s first law correct?

Answer 34

That objects naturally come to rest without an external force.

Explaining that unbalanced forces like friction cause this change in motion.

Question 35

How do normal force and gravitational force relate to Newton’s first law?

Answer 35

Normal force counteracts gravitational force, maintaining equilibrium unless an external force acts.

Question 36

What does Newton’s Second Law of Motion state?

Answer 36

It states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

Question 37

What is net force?

Answer 37

The sum of all forces acting on an object, determining the object’s motion.

Question 38

What equation represents Newton’s Second Law of Motion?

Answer 38

𝐹 = 𝑚𝑎

where:
𝐹 is the net force
𝑚 is the mass, and
𝑎 is the acceleration.

Question 39

What units are used to measure force in Newton’s Second Law?

Answer 39

Newtons (N)

1N = 1kg⋅ -9.8 m/s² acceleration, in the y-direction (due to gravity on Earth).

Question 40

What happens to net force if mass or acceleration increases?

Answer 40

If either mass or acceleration increases, the net force also increases.

Question 41

How do you calculate acceleration using Newton’s Second Law?

Answer 41

𝑎 =𝐹/𝑚

where:
𝑎 is the acceleration,
𝐹 is the net force, and
𝑚 is the mass.

Question 42

What impact did Newton’s laws of motion have on science?

Answer 42

It laid the groundwork for scientific inquiry and were foundational until the advent of quantum mechanics and relativity.

Question 43

Can an object be accelerating if it maintains a constant speed? Explain.

Answer 43

Yes, an object can be accelerating if it changes direction while maintaining a constant speed, as acceleration includes changes in velocity’s direction.

Question 44

For an object with a mass of 3.5 kg accelerating at 2.5 m/s², calculate the net force.

Answer 44

8.8N

Net force formula: 𝐹 = 𝑚𝑎
= (3.5𝑘𝑔)(2.5-9.8 m/s²)
= 8.8N

Question 45

What conditions must be met for an object to be considered at rest according to Newton’s First Law?

Answer 45

• Zero velocity.
• Balanced forces acting on it.
• No acceleration.

Question 46

What does Newton’s Third Law of Motion state?

Answer 46

It states that for every action, there is an equal and opposite reaction.

Question 47

Why do action and reaction forces not cancel each other out?

Answer 47

Because they act on different objects, not on the same object.

Question 48

What is an example of Newton’s Third Law in walking?

Answer 48

When walking, pushing against the ground (action) propels the body forward (reaction).

Question 49

Can Newton’s Third Law be used to generate energy forms other than motion?

Answer 49

Yes, it can convert mechanical energy into other forms.

e.g. electricity with a water mill

Question 50

What are three examples of Newton’s Third Law in action?

Answer 50

1. Rowboat propulsion by pushing water backward.
2. Rocket propulsion by ejecting fuel gases downward.
3. Helicopter lift from air pushed downward by its rotor.

Question 51

What is equilibrium in physics?

Answer 51

Refers to a state where all forces (and torques) acting on an object sum to zero, resulting in no acceleration.

Question 52

Distinguish between translational and rotational motion.

Answer 52

• Translational motion occurs when all points in a body move uniformly in the same direction.
• Rotational motion occurs when all points follow circular paths around a fixed axis.

Translational - e.g. sled downhill

Rotationa - e.g. spinning top or Ferris wheel

Question 53

What are the two conditions for an object to be in equilibrium?

Answer 53

1. Translational equilibrium: The sum of external forces is zero.
2. Rotational equilibrium: The sum of all torques is zero.