P8 Forces in Balance

Question 1

Displacement

Answer 1

Is a distance in a given direction

Question 2

How can vector quantities be represented

Answer 2

With and arrow in the dorection of the vector and the of length in proportion to the magnitude of the vector

Question 3

What can forces do to an object

Answer 3

Change its shape

Change its motion or its state of rest

Question 4

Unit for force

Answer 4

N, newtons

Question 5

Contact force

Answer 5

A force that acts on an object only when the objects touch each other

Question 6

Non-contact forces

Answer 6

A force that is required to physically touch another object to act upon it

Question 7

Contact force examples:

Answer 7

Friction
Air resistance
Stretching force (or tension)
Normal conatct forces

Question 8

Non-contact forces examples:

Answer 8

Magnetic force
Electrostatic force
Force of gravity (gravitational field strength)

Question 9

Newton’s third law

Answer 9

States that when two objects interact with each other, they exert equal but opposite forces on each other

Question 10

What do you say if resultant force is zero

Answer 10

That all forces acting upon it are balanced

Question 11

Resultant force

Answer 11

A single force that has the same effect as all the forces acting on an object

Question 12

What’s a Free body force diagram

Answer 12

It shows all the forces acting on an object without any other objects or other forces shown

Question 13

Newton’s first law of motion?

Answer 13

States that if the forces acting on an object are balanced the resultant force on the object is zero and of the object is at rest is stay stationary, but if it moving, it keeps moving at a constant speed and in the same direction

Question 14

If two forces act on an object along the same line, the resultant force is:

Answer 14

Their sum, if the forces act in the same direction

Their difference, if the foces act in opposite directions

Question 15

In this example, when using a spanner: the turning effect of the force, called the moment of the force, can be increased:

Answer 15

Incraeing the size of the force

Using a spanner with a longer handle (increase the distance)

Question 16

Whats the Moment of a force?

Answer 16

A measure of the turning effect of the force on an object

Question 17

Equation for moment of a force about a pivot?

Answer 17

M= F x d
d (perpendicular distance from the line of action of the force to the pivot)
F (force applied to the pivot)

Question 18

How to Increase moment of a force

Answer 18

Increase force

Or distance

Question 19

What can be used to exert a force that is greater than the effort

Answer 19

A lever (crowbar). Levers used in this way are known as force mulitpliers because the effort moves a much bigger load

Question 20

Centre of mass

Answer 20

(Of an object) is the point at which its mass can be thought of as being concentrated

Question 21

What happens if you suspend an object and then release it?

Answer 21

It will sooner or later come to rest with its centre of mass directly below the point of suspension. The object is then in equilibrium, which means it is at rest. Its weight doesn’t exert a turning effect on the object, because its centre of mass is directly below the point of suspension

Question 22

What happens of the object is turned from its suspended position and then released?

Answer 22

It will swing back to its equilibrium position, because the weight has a turning effect that returns to object to equilibrium

Question 23

When would you say and object is ‘freely suspended’?

Answer 23

If it returns to its equilibrium position after the turning force is taken away

Question 24

Where is the centre of mass of a symmetrical object?

Answer 24

Along the axis of symmetry

Question 25

Where’s the Centre of mass on a uniform ruler

Answer 25

At its midpoint

Question 26

What would you say if the object at rest doesn’t turn

Answer 26

The sum of the anticlockwise moments about any point = the sum of the clockwise moments at any point

W1d1=W2d2

Question 27

What determines wether the moments acts clockwise or anticlockwise?

Answer 27

The direction of the force and the position of the fixed point

Question 28

What are the parallelogram of forces

Answer 28

A scale diagram of two force vectors

Question 29

What is the parallelogram of forces used for

Answer 29

To find the resultant of two forces that do not act along the same line

Question 30

What is required when calculating the parallelogram of forces?

Answer 30

A protractor a ruler and sharp pencil

Question 31

What is the resultant in the parallelogram of forces

Answer 31

The resultant is the diagonal of the parallelogram that stars and the origin of the two forces

Question 32

What does resolving a force mean

Answer 32

Finding perpendicular components that have a resultant force that is equal to the force

Question 33

How to resolve a force into perpendicular directions

Answer 33

Draw a rectangle with adjacent sides along the two directions so that the diagonal represents the force vector

Question 34

What can be said about an object in equilibrium

Answer 34

The resultant force is zero

Question 35

Why is an object at rest in equilibrium

Answer 35

Because the resultant force on it is zero