Unit 3 - Dynamics

Question 1

Dynamics

Answer 1

the division of motion of mechanics that deals with the causes of motion or changes in motion

Question 2

Force

Answer 2

a push or a pull
symbol = F
unit = Newton (N)
a vector quantity

Question 3

Mass

Answer 3

the amount of matter in an object
symbol = m
unit = kg
a scalar quantity

Question 4

Weight

Answer 4

the force of gravity on an object
symbol = Fg
unit = Newton (N)
a vector quantity
measured with a spring scale

Question 5

Basic/fundamental forces

Answer 5

force of gravity
electromagnetic force
weak nuclear force
strong nuclear force

Question 6

Gravitational field strength

Answer 6

force of gravity on a 1 kg object in a specific location
g= 9.80 N/kg [d]
the value of g depends on the distance from the centre of the Earth
it decreases with increasing altitude
it decreases with decreasing altitude below Earth’s surface because of the upward force of gravity of the material above you

Question 7

Galileo and inertia

Answer 7

Galileo rolled balls down ramps and noticed that they rose to the same height on the other side
a rolling ball will continue forever unless there is a force to stop it
inertia = tendency of a body to resist changes in motion

Question 8

Newton’s First Law of Motion

Answer 8

an object will maintain the state of rest or uniform motion unless acted on by an unbalanced force
applications = pillow in pillowcase, bicycle accidents, seat belts
any unsecured objects will continue in the same direction at the original velocity

Question 9

Newton’s Second Law of Motion

Answer 9

when an unbalanced force acts on an object, it accelerates in the direction of the net force
this acceleration varies directly as the force, and inversely as the object’s mass

Question 10

Newton’s Third Law of Motion

Answer 10

for every action force there is an equal and opposite reaction force
swimming = when moving your arms backwards, you are propelled forwards
rockets in outer space = along the long axis, the forces are not balanced so the rocket accelerates forwards

Question 11

Friction

Answer 11

friction = resistance force caused by the roughness of surfaces,
unit = Newton (N)
direction is always opposite to velocity
depends on the types of surfaces and the weight of the object
when there is no acceleration, the force of friction is equal to the applied force

Question 12

Newton’s Law of Universal Gravitation

Answer 12

between every two masses in the universe, there is an attractive force of gravity
the force acts along a line joining their centres of gravity
it’s always an attractive force
the force is equal in magnitude on each mass

Question 13

Coefficient of friction

Answer 13

slope of a weight vs friction graph, no units, depends only on the surfaces

Question 14

Force of gravity

Answer 14

attractive force that exists between any two objects because of their mass, produces a direct variation

Question 15

Electromagnetic force

Answer 15

attractive or repulsive force that exists between two objects because of their charges or polarities

Question 16

Weak nuclear force

Answer 16

attractive force that keep subatomic particles (neutrons, protons) whole

Question 17

Strong nuclear force

Answer 17

attractive force that keeps atomic nucleus whole, preventing protons from flying away from each other
it is not known why any of these forces exist