Chapter 8 Forces

Question 1

Permanent magnets

Answer 1

a magnet that retains its magnetic effect for many years

Question 2

Temporary magnets

Answer 2

a magnet that stays magnetic only while it touches a permanent magnet, or one that is magnetic for a very short time

Question 3

Repulsion

Answer 3

an opposing force

Question 4

Magnetic field

Answer 4

a map of lines showing the size and direction of a magnetic force. The size of the force is shown by how close together the lines are. The direction at any point is given by the direction in which the north pole of a magnet would face

Question 5

Atoms

Answer 5

a very small particle that makes up all things. Atoms have the same properties as the objects they make up

Question 6

Negatively charged

Answer 6

The charge on an atom or object with more electrons than protons

Question 7

Positively charged

Answer 7

the charge on an atom or object with fewer electrons than protons

Question 8

Protons

Answer 8

tiny, but heavy, particle found in the nucleus of an atom. Protons have a positive electrical charge

Question 9

Neutrons

Answer 9

tiny, but heavy, particles found in the nucleus of an atom. Neutrons have no electrical charge

Question 10

Electrons

Answer 10

very light, negatively charged particles inside an atom. Electrons move around the central nucleus of an atom

Question 11

Insulators

Answer 11

materials that do not allow electric charge to flow through them

Question 12

Conductors

Answer 12

materials that allow electric charge to flow through them

Question 13

Atom

Answer 13

a very small particle that makes up all things. Atoms have the same properties as the objects they make up

Question 14

Nucleus

Answer 14

roundish structure inside cells that acts as the control centre for the cell. Plural = nuclei

Question 15

Lightning rod

Answer 15

conductive metal rod, often attached to the top of tall buildings. Lightning rods help to keep buildings safe from lightning strikes

Question 16

Electricity

Answer 16

Electric charge

Question 17

Mass

Answer 17

a measure of the amount of material in an object of substance

Question 18

Weight

Answer 18

a measure of the size of the gravity force pulling an object towards the centre of a massive body, such as the Earth. The weight of an object depends on the object’s mass

Question 19

Terminal speed

Answer 19

the constant speed reached by a falling body. A body reaches terminal speed when the force of gravity pulling it down is balanced by the air resistance pushing against it

Question 20

Air resistance

Answer 20

the force of air pushing on an object as the object moves through the air

Question 21

Newton

Answer 21

the unit for measuring forces

Question 22

Gravity

Answer 22

the force of attraction that exists between any two bodies in the universe that have mass. The gravity at the Earth’s surface is the pull on objects near its surface towards the centre of the Earth

Question 23

Friction

Answer 23

a force that acts against the movement of an object. It occurs between any surfaces that are touching and trying to move past each other

Question 24

Lubricants

Answer 24

substance with large particles that can slide easily over each other. Lubricants are used between surfaces that rub against each other to reduce wear and increase motion between the surfaces

Question 25

Traction

Answer 25

a type of friction used to assist movement

Question 26

Buoyancy

Answer 26

a force which keeps objects floating

Question 27

Surface tension

Answer 27

the ‘firmness’ of the surface of a liquid created by the attraction between particles at the surface. The surface acts like an elastic skin