2.2 - Energy

Question 1

What is gravitational potential energy (E little p in bottom corner)

Answer 1

The energy the object has by virtue of its position in a gravitational field

Question 2

What is kinetic energy (E little k in bottom corner)

Answer 2

It’s the energy an object has by virtue of its movement

Question 3

Tell me about transfers between kinetic and gravitational energy

Answer 3

As objects rise or fall, gpe can be converted to kinetic energy and kinetic energy can be converted to gravitational potential energy

Question 4

How can gpe be calculated

Answer 4

Gpe (J) = mass (kg) x gravitational field strength (N/kg) x height (m)

Height usually considered as a change in height

Gpe = mg x triangle h

Question 5

What’s the equation for kinetic energy

Answer 5

KE = 1/2 x mass x speed squared

Ke = 1/2mv^2

Question 6

Can we convert gpe to ke

Answer 6

Gpe = ke

Cause of conservation of energy

We can simplify and stuff so v = square root 2g triangle h

Question 7

Does mass affect the speed of a falling object

Answer 7

No - objects fall to the round at the same rate regardless of their mass but air resistance mean ma they done in practice

Question 8

How can we investigate finding gravity from energy conservation

Answer 8

We can convert gpe to ke

Measure the velocity that has been reached by a falling object after its fallen under gravity from a known height - then alter the height and measure the velocity and again

If we vary the height from which the object falls, the gpe is different at each bright - which can be converted to ke

If we plot a graph of change in height and v^2 on y axis we will get the gradient of the line to be 2g since v^2 = 2g x change in height

Or take a single measure from the experiment and rearrange experiment to get g - but this is prone to uncertainty from random and systematic errors

Question 9

How can the reliability of s conclusion be improved

Answer 9

Multiple readings and graphical analysis

Question 10

Define gravitational potential energy

Answer 10

Is the energy an object has by virtue of its postision in a gravitational field

Question 11

Define kinetic energy

Answer 11

The energy an object has by virtue of its movement

Question 12

What is ignored with the conservation of gpe and ke

Answer 12

The effect of air resistance

Question 13

Is anything ignored in the conservation of energy

Answer 13

No - it insists that no energy can be lost in any scenario

That mad bro

Question 14

What’s the work done

Answer 14

Th amount of energy transferred- measured in joules

Question 15

How can force be calculated when energy is transferred mechanically by the means of a force

Answer 15

Work done = force x distance moves in the direction of the force

Triangle W = F x triangle S

Question 16

Could one confuse triangle W with something

Answer 16

Yes - W for weight

DONT GET CONFUSED

Question 17

What is the work done on an object gainin gpe

Answer 17

It’s having work done on it against its weight force

W = mg

Work = force x distance = weight x height = mgtriangle h

Question 18

What direction does friction always act

Answer 18

Always acts in the exact opposite direction to movement

Question 19

How do we work out work done with a force no acting in the direction of movement

Answer 19

If we want a force and we only know weight

F = mg x cos theta

You can also use sin just make a triangle bro

Question 20

What is power definition

Answer 20

The rate of energy transfer

Or rate of work done

Question 21

What’s the formula for power

Answer 21

P =e/t

P= w/t

Question 22

What is efficiency

Answer 22

The ability of a machine to convert energy usefully

Question 23

How do we calculate efficiency / define it mathematically

Answer 23

Efficiency = useful work done / total energy input

Effiecny = total energy output / total energy input

Or efficiency = useful power output / total power output

ALWAYS LESS THAN 1

Question 24

What is the conservation of energy

Answer 24

Requires that energy can never be created or destroyed

Question 25

Define the work done

Answer 25

In a mechanical system, it’s the product of a force and the distance moved in the direction of the force

Question 26

Define energy

Answer 26

Is the property of an object that gives it the capacity to do work

A change in the amount of energy an object - could be equated to work being done - even if this is not mechanical

Question 27

Define power

Answer 27

Rate of energy transfer

Question 28

Define efficiency

Answer 28

The ability of a machine to convert energy usefully