Topic 1.5 - Forces Flashcards Preview

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Flashcards in Topic 1.5 - Forces Deck (26)
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1
Q

Define ‘resultant force’.

A

The sum of all the individual forces acting on an object (taking directions into account).

2
Q

What happens if a resultant force acts on an object?

A

It causes a change of momentum in the direction of the force.

3
Q

How can a resultant force change the motion of an object?

A

It can change…

  • Speed
  • Direction
4
Q

How can the resultant force be found?

A

Adding force vectors together, tip (arrow) to tail.

5
Q

What happens if there is zero resultant force?

A

The object will remain stationary, or (if moving) will continue to move in the same direction with the same speed.

6
Q

Define friction.

A

Friction is the force providing resistance to the motion of two surfaces sliding past each other.

7
Q

Give an example of a frictional force.

A

Air resistance.

8
Q

When work is done overcoming friction, what occurs?

A

Energy is dissipated, resulting in heating.

9
Q

When does circular motion occur?

A

When a force is acting perpendicular to the motion of an object.

10
Q

Describe the speed and velocity of an object in circular motion

A
  • The speed is constant
  • The velocity is always changing, since it is constantly changing direction
11
Q

Give an example of a force causing circular motion

A

Gravity, which causes the earth to orbit the sun.

12
Q

State Hooke’s law

A

The force on an object (eg. a wire or spring) is directly proportional to its extension.

13
Q

Give the equation for Hooke’s law

A

F = kx Where… F = force (N) x = extension (m) k = spring constant (N/m)

14
Q

At what point does Hooke’s law no longer apply?

A

The limit of proportionality

15
Q

What does the limit of proportionality look like on an extension-load graph?

A

Where the graph stops being linear.

16
Q

What is a moment?

A

The rotational (or turning) effect of a force.

17
Q

Give the equation for moments.

A

moment (Nm) = force (N) x distance (m)

18
Q

When does rotational equilibrium occur?

A

When the sum of clockwise moments = the sum of anticlockwise moments

This is the principle of moments.

19
Q

When is equilibrium reached?

A

When there is no resultant force or turning effect. (clockwise = anticlockwise moments)

20
Q

What is a centre of mass?

A

A single point through which the force of an object’s weight acts. (This is a modelling assumption).

21
Q

What is a vector quantity?

A
  • A vector quantity has both magnitude (size) and direction.
22
Q

What is a scalar quantity?

A
  • A quantity that has only magnitude, not direction.
23
Q

Give examples of vectors

A
  • Velocity
  • Force
  • Acceleration
  • Displacement
24
Q

Give examples of scalars

A
  • Speed
  • Direction
25
Q

Describe how resultant forces can be represented visually

A
  • Add force vectors tip to tail
  • Connect them for the resultant force
26
Q

Draw an extension load graph and idenitfy when hooke’s law stops being obeyed

A