2B1 Forces and Motions

Question 1

Define:

Motion

Answer 1

The change in the position of an object over time.

It occurs when an object moves from one place to another and can be described in terms of displacement, velocity, and acceleration.

Question 2

What is one-dimensional motion?

Answer 2

Motion along a straight line.

The object moves in only one direction, like a car driving down a straight road.

Question 3

What is motion in two dimensions?

Answer 3

Motion in a plane (horizontal and vertical).

This kind of motion involves movement in both the x and y directions, such as a projectile launched into the air.

Question 4

True or False:

In one-dimensional motion, an object can only move forwards or backwards.

Answer 4

True

One-dimensional motion is restricted to a single axis, meaning the object only moves in one direction.

Question 5

What is displacement?

Answer 5

Shortest distance from start to end, with direction.

It is a vector quantity because it considers both the distance and the direction of the straight line between the starting and ending points.

Question 6

How is distance different from displacement?

Answer 6

• Distance is the total path length.
• Displacement is the straight-line distance.

Distance is scalar, while displacement accounts for direction and is a vector quantity.

Question 7

True or False:

Displacement can be zero even if distance is not zero.

Answer 7

True

Walking in a circle results in a distance traveled but zero displacement since you end where you started.

Question 8

Define:

scalar quantity

Answer 8

A quantity with only magnitude.

Scalars are described by a number (magnitude) only, without any directional component. Examples include mass, time, and temperature.

Question 9

What is speed?

Answer 9

Distance traveled per unit time.

Speed is a scalar and doesn’t account for direction, unlike velocity, which is a vector quantity.

Question 10

True or False:

Distance and displacement are both scalar quantities.

Answer 10

False

While distance is scalar, displacement includes direction and is therefore a vector quantity.

Question 11

What is the formula for calculating speed?

Answer 11

Distance / Time

It tells us how fast something moves, and is calculated by dividing total distance by total time.

Question 12

Define:

Velocity

Answer 12

The rate of change of displacement.

Unlike speed, velocity is a vector, meaning it also includes the direction of movement.

Question 13

Fill in the blank:

Acceleration occurs when there is a change in _______.

Answer 13

velocity

Acceleration is defined as any change in the object’s velocity, whether in speed or direction.

Question 14

What is the formula for acceleration?

Answer 14

a = Δv / t

Acceleration measures how quickly an object’s velocity changes over time. It is calculated by dividing the change in velocity (Δv) by the time (t) taken for this change.

Question 15

A car travels 200 meters in 10 seconds. What is its speed?

Answer 15

20 m/s

Using Speed = Distance / Time, Speed = 200 meters / 10 seconds = 20 m/s.

Question 16

Fill in the blank:

The force required to accelerate a 5 kg object by 3 m/s² is ______ N.

Answer 16

15

Use the formula Force = Mass × Acceleration. In this case, Force = 5 kg × 3 m/s², resulting in 15 N.

Question 17

True or False:

Speed is the same as velocity.

Answer 17

False

Speed is a scalar, while velocity is a vector (it has both magnitude and direction).

Question 18

What is work?

Answer 18

The transfer of energy through displacement.

Work is calculated as W = F × d × cos(θ), where F is the force, d is the displacement, and θ is the angle between them.

Question 19

True or False:

Work is done when there is no displacement in the direction of the force.

Answer 19

False

Work requires a displacement in the direction of the applied force.

Question 20

What is momentum (p)?

Answer 20

The product of mass and velocity.

Momentum is a vector and represents how much motion an object has, given its mass and velocity. It is represented by p.

Question 21

How is momentum calculated?

Answer 21

p = mv

Momentum(p) is the product of an object’s mass (m) and its velocity (v). It represents the quantity of motion an object has, and the greater the mass or velocity, the greater the momentum.

Question 22

True or False:

Momentum is a scalar quantity.

Answer 22

False

Momentum includes both magnitude and direction, so it is a vector quantity.

Question 23

Define:

Force

Answer 23

A push or pull that causes a change in motion.

It is a vector quantity and can change an object’s speed or direction.

Question 24

What are contact forces?

Answer 24

Forces acting when two objects are in direct contact.

Examples include friction, normal force, tension, and applied force.

Question 25

What is **friction**?

Answer 25

A force that **opposes motion** between surfaces. ## Footnote It depends on the nature of the surfaces and the normal force.

Question 26

# True or False: Friction **always** opposes motion.

Answer 26

True ## Footnote Friction **resists** relative motion between two surfaces, no matter the direction of movement.

Question 27

What is the **normal force**?

Answer 27

A force **perpendicular** to the surface of contact. ## Footnote It acts to **counterbalance** the weight of an object resting on a surface, preventing it from accelerating through the surface.

Question 28

How does friction **change** with surface area?

Answer 28

Friction is mostly **independent** of surface area. ## Footnote While surface area does play a role, friction is more strongly influenced by the nature of the surfaces and the normal force.

Question 29

# Fill in the blank: \_\_\_\_\_\_\_ is the **force** in a rope or string.

Answer 29

Tension ## Footnote **Tension** is a *pulling* force transmitted through flexible objects like ropes or cables when they are stretched.

Question 30

What is **projectile motion**?

Answer 30

Motion of an object under the **influence** of gravity and air resistance. ## Footnote This motion combines horizontal constant velocity and vertical acceleration due to gravity, resulting in a parabolic trajectory.

Question 31

# True or False: Horizontal and vertical motions are **independent** in projectile motion.

Answer 31

True ## Footnote The horizontal motion is **unaffected** by gravity, while the vertical motion is influenced by gravitational acceleration.

Question 32

What **shape** is the trajectory in projectile motion?

Answer 32

Parabolic ## Footnote The combination of constant horizontal velocity and accelerated vertical motion results in a curved path.

Question 33

What does **Newton’s First Law** state?

Answer 33

An object will **remain** at rest or in uniform motion unless acted upon by an external force. ## Footnote This law is also called the *Law of Inertia*. It emphasizes that objects resist changes in their state of motion unless a force causes a change.

Question 34

# Define: Inertia

Answer 34

The tendency of an object to **resist** changes in its motion. ## Footnote It is directly *related* to an object's mass; the greater the mass, the greater the inertia.

Question 35

What does the **law of inertia** explain about the motion of a car when you suddenly stop?

Answer 35

The passengers **continue** moving forward. ## Footnote According to *Newton’s First Law*, the passengers' bodies resist the change in motion and keep moving while the car stops.

Question 36

What does **Newton’s Second Law** describe?

Answer 36

The **relationship** between force, mass, and acceleration. ## Footnote It states that the acceleration of an object is *directly proportional* to the net force acting on it and inversely proportional to its mass (F = ma).

Question 37

# Fill in the blanks: According to Newton's Second Law, the **acceleration** of an object is \_\_\_\_\_\_\_ proportional to the net force and \_\_\_\_\_\_\_ proportional to its mass.

Answer 37

directly, inversely ## Footnote This relationship means that for the same force, a larger mass results in less acceleration, while more force results in more acceleration.

Question 38

# True or False: If you apply a **constant force** to two objects with different masses, the object with the greater mass will have greater acceleration.

Answer 38

False ## Footnote According to *Newton’s Second Law*, the object with the greater mass will have **less acceleration** for the same force.

Question 39

What is the **formula** to calculate force?

Answer 39

Mass × Acceleration ## Footnote This formula is *derived* from *Newton's Second Law of Motion*, stating that the force on an object is the product of its mass and acceleration.

Question 40

What is the **acceleration** of a 10 kg object when a force of 50 N is applied?

Answer 40

5 m/s² ## Footnote Using *F = ma*, we rearrange to a = F/m. So, a = 50 N / 10 kg = **5 m/s²**.

Question 41

What does **Newton’s Third Law** state?

Answer 41

For every action, there is an **equal and opposite reaction**. ## Footnote This law explains that forces always come in pairs. If object A exerts a force on object B, object B exerts an equal force in the opposite direction on object A.

Question 42

# True or False: According to Newton’s Third Law, the action and reaction forces act on the **same** object.

Answer 42

False ## Footnote The action and reaction forces act on two **different** objects, but they are always equal and opposite.

Question 43

What is the **net force** acting on a 20 kg object with an acceleration of 2 m/s²?

Answer 43

40 N ## Footnote Using F = ma, the net force is F = 20 kg × 2 m/s² = **40 N**.

Question 44

What happens when the **force on an object is doubled**?

Answer 44

The **acceleration doubles**, assuming mass is constant. ## Footnote This follows from Newton's Second Law: F = ma. When F increases, so does a, as long as m remains the same.

Question 45

# True or False: According to Newton’s First Law, an object can continue moving **forever** if no force acts on it.

Answer 45

True ## Footnote In space, with no friction or other forces, an object would continue at a *constant velocity* indefinitely.

Question 46

How do action and reaction forces **apply** when a swimmer pushes against the wall of a pool?

Answer 46

The swimmer pushes on the wall, and the **wall pushes the swimmer forward**. ## Footnote The force the swimmer exerts on the wall has an equal and opposite reaction, propelling the swimmer forward.

Question 47

# True or False: Action and reaction forces **cancel** each other out.

Answer 47

False ## Footnote According to *Newton’s Third Law*, every action has an equal and opposite reaction. However, since these forces act on separate objects, they do not cancel but instead **influence** the motion of different bodies.

Question 48

What is **centripetal acceleration**?

Answer 48

Acceleration directed toward the **center** of a circular path. ## Footnote It is calculated as a = v² / r, where v is the speed and r is the radius of the circle.

Question 49

What **provides** centripetal force?

Answer 49

Tension, gravity, or friction. ## Footnote *Centripetal force* is the net inward force that keeps an object moving in a circle, and can be provided by different forces depending on the situation (e.g., tension in a rope or gravitational force in orbit).

Question 50

# Fill in the blank: Centripetal force **keeps** an object in \_\_\_\_\_\_\_ motion.

Answer 50

circular ## Footnote Without centripetal force, objects would move in straight lines due to inertia, as described by Newton's First Law.

Question 51

# Define: Buoyancy

Answer 51

An **upward** force exerted by a **fluid**. ## Footnote Buoyancy **opposes** an object's weight, allowing it to float or sink depending on its density.

Question 52

What **principle** explains buoyancy?

Answer 52

Archimedes' Principle ## Footnote *Archimedes' Principle* states that an object **submerged** in a fluid experiences an *upward buoyant force* equal to the weight of the displaced fluid. This explains why some objects float while others sink, depending on their density relative to the fluid.

Question 53

What **determines** if an object floats or sinks?

Answer 53

Its **density** compared to the fluid’s density. ## Footnote An object will float if its density is *less* than the density of the fluid; otherwise, it will sink.

Question 54

What is the **ratio** of a substance's density to water's density?

Answer 54

Relative density ## Footnote If the *relative density* is greater than 1, the substance is denser than water; if less than 1, it's less dense.

Question 55

# True or False: Relative density is a **unitless quantity**.

Answer 55

True ## Footnote Since it’s a ratio of *two densities*, relative density has no units.

Question 56

What is the **relationship** between buoyancy and relative density?

Answer 56

If relative density is less than 1, the object **floats**; if greater than 1, it **sinks**. ## Footnote Buoyancy relies on the weight of displaced fluid, which is affected by the object's relative density.

Question 57

What is **weight**?

Answer 57

The **force** exerted on an object due to gravity. ## Footnote Unlike mass, weight can vary due to the object's location. Weight is calculated using the formula: *Weight = Mass × Acceleration* due to gravity (W = mg).

Question 58

What is the **difference** between weight and mass?

Answer 58

* **Mass** is the amount of matter. * **Weight** is the force of gravity on an object. ## Footnote Mass is constant and measured in kilograms (kg), while weight depends on the gravitational force acting on the object and is measured in newtons (N).

Question 59

# True or False: Mass **changes** depending on the location of an object in the universe.

Answer 59

False ## Footnote Mass is a scalar quantity that remains constant **regardless** of location, while weight changes depending on gravitational force.

Question 60

What **units** are used to measure mass and weight?

Answer 60

* Mass is in **kilograms** (kg) * Weight in **newtons** (N) ## Footnote The unit for weight (newtons) is derived from the formula W = mg, where g is acceleration due to gravity.

Question 61

What is the **gravitational constant** (G)?

Answer 61

6.674 × 10⁻¹¹ N·m²/kg² ## Footnote The gravitational constant is used in the equation for *Newton’s Law of Universal Gravitation*.

Question 62

# Fill in the blank: According to **Newton's Law of Universal Gravitation**, the gravitational force between two objects \_\_\_\_\_\_\_ as the distance between them increases.

Answer 62

decreases ## Footnote The force is *inversely proportional* to the square of the distance between the centers of the two objects.

Question 63

# True or False: The gravitational force between two objects **increases** if their masses decrease.

Answer 63

False ## Footnote According to the law of universal gravitation, the force increases with mass, but decreases with the square of the distance between objects.

Question 64

What is a **gravitational field**?

Answer 64

A **region** where gravity exerts an attractive force on objects. ## Footnote The strength of a gravitational field depends on the mass of the object creating the field and the distance from it.

Question 65

How does the Earth's gravity field **affect** objects near its surface?

Answer 65

It **pulls objects toward the center of the Earth**, giving them weight. ## Footnote This gravitational force is **responsible** for keeping objects, including people, anchored to the Earth’s surface.

Question 66

# True or False: A gravity field is **stronger** the farther you are from the source mass.

Answer 66

False ## Footnote The strength of the gravity field **decreases** as you move further from the source mass, following an inverse square law.

Question 67

What is the **acceleration** due to gravity on Earth (in m/s²)?

Answer 67

9.8 m/s² ## Footnote This is the *constant acceleration* that objects experience when falling freely near Earth's surface, neglecting air resistance.

Question 68

How is the force of gravity **calculated** on an object?

Answer 68

W = mg ## Footnote **Weight** is the mass of the object multiplied by the local acceleration due to gravity.

Question 69

# True or False: An object's mass is **always** greater on the Moon than on Earth.

Answer 69

False ## Footnote Mass is **constant** everywhere in the universe. What changes is the object's weight due to the difference in gravity.

Question 70

How does gravity **affect** objects in freefall?

Answer 70

It **accelerates** all objects equally without air resistance. ## Footnote This is why objects like a feather and a hammer, in a vacuum, fall at the **same** rate.

Question 71

What is the **relationship** between gravity and the orbits of planets?

Answer 71

Gravity keeps planets in their **elliptical orbits** around the Sun. ## Footnote The Sun’s gravitational pull **continuously** pulls planets, preventing them from flying off into space.

Question 72

How does the acceleration due to gravity **change** with altitude?

Answer 72

The **farther** from Earth's surface, the **weaker** the gravitational pull and acceleration. ## Footnote At high altitudes, **g** decreases slightly due to the increased distance from the Earth’s center.

Question 73

# True or False: Gravity **only** affects objects on Earth.

Answer 73

False ## Footnote Gravity is a *universal force* and affects all matter, both on Earth and throughout the universe.

Question 74

How does the mass of an object **affect** the gravitational force it exerts?

Answer 74

The **greater** the mass, the **stronger** the gravitational force it exerts. ## Footnote According to Newton's law of universal gravitation, the force increases as the mass increases.

Question 75

# Define: vector quantity

Answer 75

A quantity that has both **magnitude and direction**. ## Footnote Unlike *scalar quantities*, which only have magnitude, *vector quantities* are fully described by both the size (magnitude) and the direction in which they act.

Question 76

What are the **components** of a vector?

Answer 76

The **projections** of a vector along coordinate axes. ## Footnote Components are typically **horizontal (x)** and **vertical (y)** and can be found using trigonometry or by breaking the vector into parts.

Question 77

What is the **formula** for calculating the force from a vector?

Answer 77

F = m × a ## Footnote where: **m** is mass **a** is acceleration

Question 78

What are examples of **vector quantities**?

Answer 78

* displacement * velocity * acceleration * force * momentum

Question 79

What is the **difference** between a vector and a scalar?

Answer 79

A **vector** has both magnitude and direction; a **scalar** has only magnitude. ## Footnote Vectors include force, velocity, and displacement, while scalars include mass, temperature, and time.

Question 80

What are examples of **scalar quantities**?

Answer 80

* mass * speed * time * distance * energy

Question 81

# True or False: The magnitude of a force is **independent** of the direction.

Answer 81

False ## Footnote The direction of a force **affects** how an object moves or accelerates, making it essential to the force's impact.

Question 82

What is the **resultant** of two vectors?

Answer 82

The **vector sum** of the two vectors. ## Footnote The resultant can be found using the *head-to-tail method* or by *adding* their components.