yr 11 September recap

Question 1

Free body diagrams

Answer 1

a simple diagram that uses arrows to show all of the forces acting on an object.

The length = magnitude of the force

The direction = the direction of the force

this means that all the forces are vectors

Question 2

The resultant force

Answer 2

The resultant force is the overall force acting on an object

it has magnitude and direction

Question 3

A resultant force acts upon an object.

Which properties might be affected by that resultant force?

Answer 3

Acceleration: The object will accelerate in the direction of the force.

Velocity: The speed or direction of the object may change.
Momentum: Changes as velocity changes.

Kinetic Energy: Increases or decreases with changes in speed.

Shape: May deform if the object is flexible or elastic.

Question 4

If all the forces acting on an object balance out, then we say that the object is

Answer 4

in equilibrium

Question 5

equilibrium definition

Answer 5

when all the forces acting on an object balance out

Question 6

deformation meaning

Answer 6

when an object changes it’s shape as a result of forces being applied to it

Question 7

elastic deformation

Answer 7

when an object does return to its original shape after the forces have been removed

Question 8

inelastic deformation (or sometimes plastic deformation)

Answer 8

when an object does not return to its original shape after the forces have been removed

Question 9

Extension

Answer 9

the change in length when stretched or compressed

Be aware that it can also refer to a decrease in length, if the spring is compressed.

Question 10

What is the minimum number of forces required to stretch, compress, or bend an object?

Answer 10

2

if only 1 force is applied to an object then it will just move, it won’t stretch, compress, or bend.

e.g if you press down on a stress ball, a force is being exerted down on the ball by you. However there is also the floor exerting a force upwards on the ball at the same time making it 2 forces ;)

Question 11

Which object do you think has the higher spring constant?

A bungee cord or a plank of wood

and why?

Answer 11

the plank of wood higher since it requires more energy to stretch it or, in other words, is more stiff (less elastic).

Question 12

spring constant
+ units

Answer 12

spring constant is a measure of how many Newtons of force it would require to stretch (or compress) the object by 1 metre. It has the units N/m.

higher the spring constant = more stiffer material

Question 13

Hooks law can be described by the formula. What is the formula?

Answer 13

F=ke

• F = force applied (N)
• 𝑘 = the spring constant (stiffness of the spring) (N/m)
• e = the extension or compression of the spring from its natural length. (m)

Question 14

The elastic limit

Answer 14

The point at which an object being stretched stops deforming elastically, and starts deforming inelastically.

Question 15

what could happen if you stretched an object too much

Answer 15

it can pass its ‘elastic limit’ (also known as the ‘limit of proportionality’).

Question 16

what’s the statement of hooks law (+ symbols)

Answer 16

F ∝ e
force is directly proportional to extension

Question 17

Force is measured in what?

Answer 17

newtons (N).

Question 18

force, acceleration, mass formula
triangle

Answer 18

triangle
f/
m x a

Question 19

why do sports cars have big engines and are made using light materials ?

Answer 19

Because the lighter the material the less force is needed to accelerate the car. reduces inertia

Question 20

terminal velocity definition

Answer 20

Terminal velocity is the constant speed reached by a falling object when the force of gravity is balanced by air resistance, resulting in zero acceleration.

Question 21

Which equation links acceleration (a), mass (m) and resultant force (F)

Answer 21

F=ma