Newtons Laws

Question 1

Newton’s First Law

Answer 1

INERTIA!
An object at rest will remain at rest unless acted on by an unbalanced force and an object travelling with a constant speed in a straight line will continue to do so unless acted on by an unbalanced force.

Question 2

Newton’s Second Law

Answer 2

The acceleration of an object is directly proportional to the unbalanced force applied.

Question 3

Newton’s Third Law

Answer 3

For every action force F1 There is an equal but opposite reaction force F2.

F1 = -F2

Question 4

Average speed formula

Answer 4

v = s /t
t = s / v
s = vt

Question 5

Kmh-1 to ms-1

Answer 5

divide by 3.6

Question 6

ms-1 to kmh-1

Answer 6

times by 3.6

Question 7

Acceleration formula

Answer 7

a = v - v0 / t
a = acceleration
v = final speed
v0 = initial speed
t = time

v = v0 + at
t = v - v0 / a

Question 8

Newton’s second Law formula

Answer 8

> Fres = ma

> Don’t forget to say LEFT or RIGHT in some

Question 9

Another way of writing Newton’s second law…..

Answer 9

Fres = ^p / ^t

Question 10

Physics of the airbag

Answer 10

When a car undergoes a front end collision, the airbag explosively inflates so that it is fully inflated in front of the driver before the driver reaches it
The face of the driver pushes into the airbag causing it to deflate “slowly”
This increases the time it takes for their face to come to rest and therefore reduces the force on their face

Question 11

Increasing time it takes to come to rest

Answer 11

If a netball is thrown across the court at another players chest with strong force the player will catch it with two hands and to increase the time the netball takes to come to rest the player will catch the ball in front of their chest and swing their arms backwards in one swift movement, reducing the momentum of the ball and force needed to bring its movement to rest.

Question 12

Decrease the time it takes to come to rest

Answer 12

If a wood chopper is using an axe to cut wood, to be able to slice it straight threw the wood chopper has to swing the axe with lots of force, therefore reducing the time it takes for the axe to come to rest.

Question 13

Newton’s third law helicopter example

Answer 13

F1 is the blades pushing the air down and F2 is the air pushing the blades up.

Question 14

Skaters example

Answer 14

Part 1 is Newton’s 1st Law (at rest until acted on)
Part 2 is Newton’s 2nd Law (larger force applies, larger acceleration)
- large mass is a smaller acceleration and small mass is larger acceleration
- F = mA = Ma
The whole image put together is Newton’s 3rd Law (opposite reactions)

Question 15

What does the crumple zone do ?

Answer 15

The crumple zone increases the time to come to rest. Thus the force needed to bring the passenger to rest is reduced. So the chances of injury are reduced and force is also reduced.

Question 16

Why seatbelt?

Answer 16

In a head on collision the car stops but the passenger continues at the same speed and hits the inside of the car increasing injury. If the seatbelt is on it provides the unbalanced force to stop the passenger. It applies a force over the robust parts of the body (hips & sternum) ie less injury.

Question 17

Distance ( s ) is what ?

Answer 17

Is a measure of how far something is away from something else and is measured in metres ( m )

Question 18

Displacement ( š ) is

Answer 18

The distance travelled in a certain direction from a given reference point

Eg: we have all gone to Victoria square
12.4km northeast from sacred heart college

Question 19

Motion graphs always have ( t ) on the horizontal axis

Answer 19

Positive slope: constant speed AWAY from the reference point
Negative slope: constant speed TOWARDS the reference point
No slope (horizontal): at rest away from the reference point 

A straight diagonal s vs t graph represents CONSTANT SPEED
The steeper the graph the greater the speed

Question 20

Work

Answer 20

> Work ( W ) is done whenever a force ( F ) acts on an object and that object moves a distance ( s ) in the direction of that force
Work is measured in JOULES
W = Fs

Question 21

Weight

Answer 21

> A FORCE measured in NEWTONS ( N )
Weight ( wt ) is the product of mass ( m ) of an object and the acceleration ( g ) due to gravity
wt = mg

> wt = weight ( N )
m = mass ( kg )
g = acceleration due to gravity ( ms-2)
9.8 ms-2

Question 22

Headrest

Answer 22

• Consider a passenger at rest in a stationary car without a headrest. When the car is hit from behind an unbalanced force is provided the seat that pushes the passengers body forwards. The head remains at rest. Until the neck provides the unbalanced force needed to make it catch up with the body. This can cause neck injury or death.
• A headrest provides the unbalanced force that causes the head to move forward at the same time the body does, thus avoiding injury.