Grade 8 Science: Exploring Forces

Vocabulary practice flashcards covering fundamental concepts, definitions, units, types of forces, weight, mass, buoyancy, and experiments from Grade 8 Science Chapter 5: Exploring Forces.

Force

A push or pull on an object resulting from its interaction with another object.

Newton ($\text{N}$)

The SI unit of force, written with a lowercase 'n' when spelled out and denoted by the capital letter symbol 'N'.

Balanced Forces

Forces acting on an object at rest that balance one another so that no change in motion occurs.

Contact Force

A type of force that acts only when there is physical contact, direct or indirect, between the interacting objects.

Muscular Force

A contact force resulting from the action of muscles in the body as they contract and elongate during physical activity.

Muscular Force in Digestion

The internal force generated by muscles to chew food and push it through the alimentary canal during the digestive process.

Muscular Force in Circulation

The force generated by the expansion and contraction of heart muscles that circulates blood throughout the body.

Force of Friction

A contact force that comes into play when an object moves or attempts to move over another surface, always acting opposite to the direction of motion.

Surface Irregularities

Minute microscopic bumps and roughnesses present even on smooth surfaces that interlock with each other to cause friction.

Fluid Friction

The resistive frictional force exerted by liquids and gases (such as water and air) on objects moving through them.

Streamlined Shaping

The design of specific, streamlined shapes for objects like aeroplanes, ships, boats, and high-speed trains to reduce fluid friction.

Non-contact Force

A category of forces whose effects can be exerted and experienced at a distance without any physical contact between the objects.

Magnetic Force

A non-contact force of attraction or repulsion exerted by a magnet on another magnet or on a magnetic material.

Like Magnetic Poles

Magnetic poles of the same kind (North–North or South–South) that repel each other when brought close.

Unlike Magnetic Poles

Magnetic poles of different kinds (North–South) that attract each other when brought close.

Static Charges

Electrical charges that accumulate on the surfaces of certain materials through rubbing and do not move by themselves.

Charged Object

An object that has acquired static electrical charges on its surface, enabling it to exert a force on other charged or uncharged bodies.

Electrostatic Force

A non-contact force exerted by an electrically charged body on another charged body or an uncharged body.

Positive and Negative Charges

The two kinds of static electrical charges; like charges repel one another while unlike charges attract one another.

Electric Current

The flow of electrical charges in a circuit, which can produce lighting, heating, or magnetic effects.

Gravitational Force (Gravity)

The non-contact attractive force with which the Earth pulls objects towards itself; it is always an attractive force.

Vertical Motion

The straight vertical movement of an object upwards or downwards under the influence of gravitational force.

Weight

The gravitational force with which the Earth (or another planet) attracts an object towards itself, measured in newtons ($\text{N}$).

Mass

The amount of matter contained in an object, measured in grams ($\text{g}$) or kilograms ($\text{kg}$), which remains constant everywhere.

Spring Balance

A mechanical device consisting of a spring fixed at one end with a hook at the other, used to measure weight and mass via spring extension.

Least Count of a Spring Balance

The smallest value of weight that a spring balance can read, determined by dividing the difference between two main scale marks by the number of small subdivisions ($\frac{1\,\text{N}}{5} = 0.2\,\text{N}$).

Weight of $1\,\text{kg}$ on Earth

The force of gravitational pull exerted on a $1\,\text{kg}$ mass on Earth, which equals $10\,\text{N}$.

Weight of $1\,\text{kg}$ on the Moon

The gravitational pull on a $1\,\text{kg}$ mass on the Moon, which equals $1.6\,\text{N}$ (approximately one-sixth of its weight on Earth).

Weight of $1\,\text{kg}$ on Mars

The gravitational pull exerted on a $1\,\text{kg}$ mass on Mars, which equals $3.8\,\text{N}$.

Weight of $1\,\text{kg}$ on Venus

The gravitational pull exerted on a $1\,\text{kg}$ mass on Venus, which equals $9\,\text{N}$.

Weight of $1\,\text{kg}$ on Jupiter

The gravitational pull exerted on a $1\,\text{kg}$ mass on Jupiter, which equals $25.4\,\text{N}$.

Beam Balance

An instrument used to find the mass of an object by comparing its gravitational pull directly against standard known masses.

Buoyant Force (Upthrust)

The upward force exerted by a liquid on an object that is placed or submerged in it.

Condition for Floating

The equilibrium state achieved when the upward buoyant force exerted by a liquid equals the downward gravitational force (weight) of the object.

Condition for Sinking

The state that occurs when the downward gravitational force acting on an object is greater than the upward buoyant force exerted by the liquid.

Archimedes' Principle

The principle stating that an object immersed fully or partially in a liquid experiences an upward force equal to the weight of the liquid it displaces.

Pumice

A light, porous volcanic rock formed with trapped gas bubbles during rapid cooling of lava that has a lower density than water and floats.

Electroscope

A scientific apparatus comprising a jar, lid, straw, copper wire, and aluminium foil leaves used to determine whether an object is electrically charged.

Effects of Force on Motion

The capacity of an applied force to move a stationary object, change the speed of a moving object, or alter its direction of travel.

Effect of Force on Shape

The deformation or alteration in an object's physical form produced when a force is applied (such as pressing an inflated balloon or rolling chapati dough).