Chapter 4 + some chapter 3

Question 1

What is a free body diagram?

Answer 1

A singular object with all its forces drawn on it.

Question 2

What is the net force?

Answer 2

The vector sum of all forces acting on an object.

Question 3

What is the general principe of the equation f=ma

Answer 3

A more massive objects requires more force to change the velocity.

Question 4

What is intertia?

Answer 4

How hard it is to change the objects velocity.

Question 5

What is weight?

Answer 5

A downwards force due to mass being in a gravitational field.

Question 6

What is friction?

Answer 6

The force when two objects make contact with each other, it opposes Motion and acts in the opposite direction of movement.

Question 7

What is drag?

Answer 7

It opposes the motion of an object while moving through a fluid.

Question 8

What is upthrust?

Answer 8

An upwards force on an object in a fluid.
- depends on density

Question 9

What is the normal contact force?

Answer 9

When two objects touch, it is constant and perpendicular to the surface.

Question 10

What is tension?

Answer 10

The force that acts along a string/rope, thrust is the opposite of tension.

Question 11

What is the centre of mass?

Answer 11

The point where the weight appears to act on an object.

Question 12

Does the centre of mass of an object have to be inside the object?

Answer 12

No.

Question 13

How do you find the centre of mass of a shape?

Answer 13

1. Pin it up so it can hang freely
2. Draw a line vertically downwards from where it hangs, use a plum to determine this
3. Repeat this step minimum three times, all lines should intersect at the centre of mass

Question 14

What is the formula for density?

Answer 14

mass/volume, m/v

Question 15

What is the density of water?

Answer 15

1000kgm(-3)

Question 16

What is the density of air?

Answer 16

1.3kgm(-3)

Question 17

What is the formula for pressure?

Answer 17

force/area, f/a

Question 18

What is the unit for pressure?

Answer 18

Pascals

Question 19

What is the formula for density of a fluid above an object?

Answer 19

P(rho)=pgh

Question 20

What is upthrust in terms of weight?

Answer 20

The weight of the fluid displaced by the object.

Question 21

What is the formula for upthrust?

Answer 21

p(rho)gv

Question 22

What is a moment?

Answer 22

a force that causes something to rotate.

Question 23

What is the equation for a moment?

Answer 23

force multiplied by the perpendicular distance from the hinge.

Question 24

What are the units for a moment?

Answer 24

Nm.

Question 25

What is the principle of moments?

Answer 25

For an object at equilibrium, the sum of the clockwise moments equals the sum of the anticlockwise moments.

Question 26

How do you work out a moment when the force isn’t perpendicular to the hinge?

Answer 26

Split the force vector up to find the perpendicular distance.

Question 27

What is a couple?

Answer 27

Two forces of equal magnitude acting in opposite directions, not acting along the same line.

Question 28

What is the equation and unit for torque?

Answer 28

Force multiplied by distance, measured in Nm

Question 29

How do you find the torque of a couple?

Answer 29

One of the forces multiplied by the distance between them.

Question 30

What is the simplified definition for torque?

Answer 30

The rotational force that causes and object to turn or twist.

Question 31

When does triangle of forces apply?

Answer 31

When there is 3 forces acting on an object.

Question 32

What are the methods of solving triangular forces problems?

Answer 32

1. Nose to tail diagrams
2. Finding the horizontal and vertical components of the vectors