P8 - Forces In Balance

Question 1

What is displacement?

Answer 1

Distance without a change in direction

Question 2

What is a Vector?

Answer 2

Physical quantities with size (magnitude) AND direction

Question 3

What is a scalar?

Answer 3

Physical quantities with size but NO direction

Question 4

Wind blowing at 20 mph, vector or scalar?

Answer 4

Scalar

Question 5

Car travelling east at 80 mph, vector or scalar?

Answer 5

Vector

Question 6

Newton’s third law?

Answer 6

When two objects interact with each other they exert equal and opposite forces on each other.

Question 7

Friction is….?

Answer 7

Friction is a force between two surfaces that are sliding, or trying to slide, across each other.

Question 8

Definition of Weight?

Answer 8

The force of gravity pulling things downwards. It makes things fall, and keeps things on the ground.

Question 9

Definition of Reaction?

Answer 9

It pushes things upwards when they are in a liquid. It pushes boats upward so that they do not sink.

Question 10

Definition of Thrust?

Answer 10

A forward force, from an engine for example.

Question 11

Definition of Air resistance?

Answer 11

It tries to stop things moving through the air. It pushes leaves and parachutes upwards so that they fall slowly.

Question 12

Definition of Upthrust?

Answer 12

It stops things from going right through solid objects. When this force acts from your chair it pushes you upwards so that you do not fall through it.

Question 13

Moment definition?

Answer 13

A turning effect of a force (Force x distance)

Question 14

How to increase the moment?

Answer 14

Increase the force applied, or increase the perpendicular distance from the pivot.

Question 15

2 types of force multipliers

Answer 15

Opposite side force multiplying levers and Same side force multiplying levers.

Question 16

Moment of Gears

Answer 16

Force x gear radius

Question 17

Centre of mass

Answer 17

Centres of mass typically lie on lines (or planes) of symmetry of objects.

Question 18

Principle of moments

Answer 18

The sum of all the clockwise moments about any point = The sum of all the anticlockwise moments about that point

Question 19

How to find the horizontal and vertical components of a force.

Answer 19

Horizontal = Force x cos (angle)
Vertical = Force x sin (angle)

Question 20

How do you find the centre of mass of an irregular shape?

Answer 20

You would hang the shape, made out of card, from a thread with a plumb line attached to it and you will use a pencil and ruler to draw the line that the plumb line makes on the piece of card and rotate the card and repeat the process. The lines will all meet on one point, and that is the centre of mass