P8 - Forces in Balance

Question 1

define vector

Answer 1

a value that has a magnitude and a direction

Question 2

define scalar

Answer 2

a value that only has a magnitude

Question 3

define magnitude

Answer 3

the size of a quantity

Question 4

What does a force diagram show?

Answer 4

It shows the magnitude and direction of a force.

Question 5

define Newton’s 1st law of motion

Answer 5

An object remains in the same state of motion unless a resultant force acts on it

Question 6

define Newton’s 2nd law of motion

Answer 6

F = ma
As a resultant force acts on an object, it will accelerate

its speed and or direction will change

Question 7

define Newton’s 3rd law of motion

Answer 7

For every action, there is an equal and opposite reaction

Question 8

formula moment

forces

Answer 8

moment = effort * dist from pivot
Nm = N * m

Question 9

What are levers?

Answer 9

force multipliers

Question 10

What do levers do?

Answer 10

they reduce the effort needed to move the load by increasing the distance over which it acts.

effort - force

Question 11

define the principle of moments

Answer 11

sum of anticlockwise moments = sum of clockwise moments

Question 12

Explain how low and high gears work in cars

Answer 12

A low gear has a higher turning effect but a lower rotational speed.
A high gear has a lower turning effect but a higher rotational speed.

Question 13

Method to solve for the resultant force in a force diagram

Answer 13

draw a parallelogram using a compass, then use a ruler to measure the distance

Question 14

define centre of mass

Answer 14

the point (in space) at which all the mass of an object seems to be concentrated

Question 15

define centre of gravity

Answer 15

the point (in space) at which all the weight of an object seems to act.

Question 16

Method to find the centre of mass of a regular shape

Answer 16

the centre of mass is the point where the lines of symmetry cross

Question 17

Method to find the centre of mass of an irregular shape

Answer 17

Hang the object and draw a straight line down the direction in which weight acts, do this a second time hanging it from a different point.
Where these 2 lines intersect is the centre of mass.

Question 18

define freely suspended

Answer 18

when an object returns to a point of equilibrium after a turning force is taken away

Question 19

Is the centre of mass and gravity the same in an object?

Answer 19

Not always, they are the same only if there is a uniform gravitational field.