Topic 1 Forces And Motion

Question 1

Newtons first law of motion

Answer 1

An object remains at rest, or moves in a straight line at constant speed, unless it is acted on by an unbalanced force.

Question 2

Speed equation

Answer 2

Speed(v) = distance(d) / time(t)

Question 3

Equilibrium definition (force)

Answer 3

Any object that is subject to balanced forces is said to be at equilibrium.

Question 4

Static equilibrium definition

Answer 4

When an object remains at rest.

Question 5

Dynamic equilibrium definition

Answer 5

If an object is moving with a constant speed and direction.

Question 6

Weight definition

Answer 6

The force due to gravity close to the surface of the earth is known as weight and has a magnitude given by:

Weight = mass x acceleration due to gravity (W = mg)

Units m/s^2

Earths gravity is 9.81 m s^-2

Question 7

Hooke’s law

Answer 7

Applied force = constant x extension (Fstr = ks x)

The spring constant quantifies the size of extension produced by a given force.

Rearranged:

ks = Fstr / x

Question 8

Free body diagrams

Answer 8

A way of presenting all the forces acting on a single object, without the clutter of any surrounding objects.

Arrows point away from the object in the direction the force is being applied. Equal forces require equal sized arrows.

Question 9

Normal reaction force definition

Answer 9

The reaction force that keep a solid object from falling through the surface it sits on. The force is perpendicular to the surface.

When an object is placed on a surface it compresses the atoms of the surface together. This acts like a sort of spring that pushes back against an object.

Question 10

Tension definition

Answer 10

The force in a string or other flexible one-dimensional object that is caused by the force applied to its ends.

Question 11

Frictional force definition

Answer 11

The force due to the interaction of an object and the surface it sits on. Affected by surface roughness and chemical reactions between surfaces.

Question 12

Maximum frictional force

Answer 12

Ffric = μN

Maximum frictional force (Ffric) is the point where the force of friction can no longer balance applied force. (Newtons)

Coefficient of friction (μ) is a value which depends on the properties of both object and surface. (No units)

N Is the size of the normal reaction force between the object and surface. (Newtons)

Question 13

Normal reaction/weight equation

Answer 13

N = mg

Normal reaction (or weight) = mass x gravity

Question 14

What’s a component?

Answer 14

The part of a force that acts in a given direction, parallel to a given axis.

Question 15

Resolving forces

Answer 15

The process of identifying the components of a force that are parallel and perpendicular to a given direction

Question 16

Acceleration definition

Answer 16

This is the rate of change in velocity measured in m/s/s. It has a magnitude and direction associated with it like velocity.

Question 17

Acceleration equation

Answer 17

Average acceleration= ( change in speed (final speed-initial speed)) / time taken to change speed.

A = (v-u) / t

Question 18

Newtons second law of motion

Answer 18

The total force applied to an object is equal to the mass of the object times the acceleration.

Applied force = mass x acceleration

F = ma

The acceleration is in the same direction as the force.

Question 19

Newtons third law

Answer 19

Every action has an equal and opposite reaction.

Question 20

Electric charge definition

Answer 20

A fundamental property of matter. There are two types of charge, positive and negative. Like charges repel and unlike charges attract.

If matter has an equal number of positive and negative charge particles then it is said to be electronically neutral.

Charge is measured in coulomb (C).

Question 21

Electric force definition

Answer 21

The force produced on a charged object by another electric charge. The electric force between the two objects depends on Coulomb’s law.

Question 22

Coulomb’s law

Answer 22

Describes the electric force between 2 objects.

F el = ke ((Q1 Q2)/r^2)

Q1 and Q2 represent the value of the two charges and r to represent the distance between them.

ke is a constant with a value of 8.99 x10^9 N m^2 C^-2

Question 23

Electric field definition

Answer 23

The region where electronic forces act, produced by a stationary electric charge or by a varying magnetic field.

Question 24

Calculate electric force using an elective field

Answer 24

Electric force can also he calculated with the equation.

F el = Qε

Where F el is electric force, Q is the charge of an object and ε is the strength of the electric field.

Question 25

Uniform electric field definition

Answer 25

This is when there is a consistent force over a relatively large region.