Topic 8 - Energy - Forces Doing Work

Question 1

work done

Answer 1

The energy transferred by a force

Question 2

Work done equation

Answer 2

Work done (J) = force (N) x distance moved in the direction of the force (m)

Question 3

power (watts)

Answer 3

The rate at which energy is transferred

Question 4

Power equation

Answer 4

Power (W) = work done (J)
time taken (s)

Question 5

Contact forces

Answer 5

Forces exerted on each other when the objects are touching

Question 6

Normal contact force

Answer 6

The reaction force acts at right angles to the surface (e.g. when you stand on the floor there is an upwards force from the floor on you)

Question 7

Gravity

Answer 7

Force that occurs between any two objects that have mass

Question 8

Forcefield

Answer 8

Space around an object where it can affect other objects

Question 9

Magnetic field

Answer 9

Space around magnet where it can affect other materials

Question 10

Electric field

Answer 10

An object charge of static electricity has an electric field around it

Question 11

A free body force diagram

Answer 11

A diagram showing the forces acting on the object

Question 12

How do you work out a resultant force using a scale diagram?

Answer 12

• draw arrows of the correct angles to represent the forces the length of each arrow should represent the size of the force
• Draw lines to make a parallelogram
• The resultant forces is a diagonal of the parallelogram measure this arrow to work out the size of the resultant force

Question 13

How can use a scale diagram to resolve the forces on an object?

Answer 13

• Draw a force arrow to scale at the correct angle
• Draw a rectangle with the sides in the direction you are interested in (e.g. Horizontal and vertical)
• The resolved forces are the size of the rectangle

Question 14

Moment

Answer 14

the Turning force

Question 15

What is the moment of a force depend on?

Answer 15

The size of the force and where the force is applied

Question 16

pivot

Answer 16

the point around which the object can rotate or turn

Question 17

Moment of a force equation

Answer 17

Moment of a force (Nm) = force (N) x distance normal (perpendicular) to the direction of the force

Question 18

What is the distance normal?

Answer 18

The distance between the force and the pivot is measured normal (at right angles) to the direction of the force

Question 19

When will an object balance? (In equilibrium)

Answer 19

• When the anticlockwise moment from the goods is equal to the clockwise moment from the weights
• The sum of clockwise moments = the sum of anticlockwise moments

Question 20

lever

Answer 20

A bar that pivot is about a point and is used to transfer a force