Work Done

Question 1

Work done?

Answer 1

When a force moves on an object through a distance, work is done on the object and energy is transferred

Question 2

Equation for work done?

Answer 2

E = F x d

E =work done, F = Force, d = distance moved in direction of the force

Question 3

What does work done often cause?

Answer 3

A rise in temperature as energy is dissipated to the thermal energy stores of the moving object and the surroundings
-efficiency is reduced

Question 4

What is power?

Answer 4

The rate of energy transfer

-the anger the power the more work is done per second

Question 5

Equation for power?

Answer 5

Power = work done (J)/ time take (s)

Question 6

What is a moment?

Answer 6

A turning effect of a force

Moment of force (Nm) = Force (N)x perpendicular distance (m)

Question 7

What is the effect of having a larger distance from the pivot and not being at right angles?

Answer 7

Larger moment

-if not at 90° then the moment would mean a smaller distance and so smaller moment

Question 8

What is the principle of moments and what does it mean?

Answer 8

The sum of the clockwise moments = the sum of the anti-clockwise moments
-this is for an object to be in equilibrium

Question 9

How do levers make it easier for us to do work?

Answer 9

Levers transfer the turning effect of a force
-they increase the distance from the pivot at which a force is applied so the smaller the force needed to give the same moment

Question 10

How do gears use moments?

Answer 10

• there teeth interlock so one causes the other to turn in the opposite direction
• they are used to transmit the rotational effect of a force from one place to another

Question 11

What gears have smaller or bigger moments?

Answer 11

• a force applied to a small gear creates a small moment
• this gear applies the same force to the next gear
• if the next gear is larger the force is applied further away from the pivot so moment is larger
• they rotate at different speeds, larger gear the slower the speed

Question 12

How do you work pit speeds and moment in gears?

Answer 12

• look at gear ratio
• e.g, if one larger one had 16 teeth and another smaller 8 ratio is 2 to 1
• so for every one turn of the larger gear the smaller will do 2
• moments is double size in the bigger one

Question 13

What is a contact force?

Answer 13

The forces exerted between two objects when they touch

E.g. friction and normal contact force

Question 14

What is a non-contact Force?

Answer 14

Forces that act between objects that aren’t touching

-e.g. gravitational force and magnetic