3.2 Forces In Action

Question 1

Newton’s second law.

Answer 1

F= ma

Question 2

What are the four fundamental forces of nature?

Answer 2

• gravitational force
• electromagnetic force
• weak interaction
• strong interaction

Question 3

Which is the weakest of the four fundamental forces?

Answer 3

Gravitational

Question 4

What does the electromagnetic force do?

Answer 4

Holds atoms and molecules together.

Question 5

How can the electromagnetic force be described?

Answer 5

The exchange of photons between charged particles of magnetic materials.

Question 6

What is the weak interaction responsible for?

Answer 6

Radioactive decay.

Question 7

What is the range of the weak interaction?

Answer 7

10-18m

Question 8

What is the strong interaction responsible for?

Answer 8

Holding subatomic particles together.

Question 9

What is the strongest fundamental force of nature?

Answer 9

The strong interaction.

Question 10

What is the range of the strong interaction?

Answer 10

10-15m

Question 11

What are the five main types of force we need to know about?

Answer 11

Tension, normal contact force, upthrust, friction and drag.

Question 12

What is the equation for tension?

Answer 12

Tension = mass x acceleration.

Question 13

What is upthrust?

Answer 13

The upwards force that a liquid or gas exerts on a body floating in it due to the water displaced.

Question 14

When will an object move at terminal velocity?

Answer 14

When the magnitude of the body’s weight becomes equal to the sum of the drag and the upthrust and the resultant force is 0.

Question 15

What is a fluid?

Answer 15

A liquid or a gas.

Question 16

What is p in the equation for drag?

Answer 16

The density of the fluid.

Question 17

What is A in the equation for drag?

Answer 17

The cross sectional area of the moving object

Question 18

What is v in the equation for drag?

Answer 18

Velocity of moving object.

Question 19

What is equilibrium?

Answer 19

When all the Coplanar forces are balanced.

Question 20

How can we work out the resultant of two forces acting on a body?

Answer 20

• a scale drawing

- right angled vector triangle.

Question 21

What does a triangle of forces represent?

Answer 21

The direction and magnitude of three coplanar forces that are acting on an object in equilibrium.

Question 22

Equation for turning moment?

Answer 22

Magnitude of force (N) x perpendicular distance from a fixed point (m)

Question 23

Unit of turning moment?

Answer 23

N m

Question 24

Define moment of force or turning moment.

Answer 24

The product of the and perpendicular distance of its kind of action from the point or axis.

Question 25

What is the fancy name of the pivot?

Answer 25

Fulcrum

Question 26

Define the principle of moments.

Answer 26

For an object to in rotational equilibrium, the sum of the clockwise moments about a point must be the sum of the anti-clockwise moment about the same point.

Question 27

What are the two conditions for equilibrium?

Answer 27

1) resultant force on the objects must be 0 | 2) sum of clockwise = sum of anti-clockwise

Question 28

What is drag?

Answer 28

Friction force experienced by an object travelling through a fluid.

Question 29

What is Archimedes principle?

Answer 29

A law stating that a body totally or partially immersed in a fluid is subject to an upward force equal in magnitude to the weight of fluid it displaces.

Question 30

When does a couple occur?

Answer 30

When two equal, antiparallel forces act to produce rotation - no linear motion occurs.

Question 31

What is a torque?

Answer 31

The moment or turning effect of a couple | The product of one of the forces and the perpendicular distance between them

Question 32

What are the units of turning moment (torque)?

Answer 32

N m

Question 33

How do you calculate the turning moment produced by a couple?

Answer 33

One of the forces multiplied by their separation.

Question 34

What factors affect drag?

Answer 34

Cross sectional area | The density of the fluid

Question 35

What is the centre of mass?

Answer 35

The single point at which all of the mass of the object can be assumed to be situated.

Question 36

What happens if a forces acts directly on the centre of mass?

Answer 36

Move in a straight line.

Question 37

What happens if a force does not act on the centre of mass?

Answer 37

Move with an added rotational motion.

Question 38

What is the centre of gravity?

Answer 38

Single point through which the entire weight of the object can be thought to act.

Question 39

Define the Newton.

Answer 39

Force is 1N when 1kg of mass has an acceleration of 1ms-2

Question 40

Equation relating velocity and drag

Answer 40

Fd=kv^2

Question 41

Equation for pressure

Answer 41

Hpg