What is the connection? Projectile motion

What is the connection?

Projectile motion

Which equations can be used to describe the motion of projectiles?

What force acts on an upward moving projectile?

First, think about…

When the ball is stationary, what forces are

acting on it?

Remove the hands and…?

What happens to the ball?

What forces are acting on the ball?

Air resistance is negligible

Describe the motion using the words velocity,

acceleration and displacement.

Explain in terms of forces.

Sketch the velocity–time and acceleration–time

graphs of the motion.

Include values on the axes.

What force acts on an upward moving projectile?

Initial vertical velocity of a ball dropped from a height?

A ball thrown up in the air.

Vertical velocity at maximum height?

A ball thrown up in the air.

Is it on its way up or down?

For a ball which is thrown up and allowed to fall back to exactly the same point…

…the downward motion will mirror the upward motion.

How will initial vertical velocity and final vertical velocity compare in magnitude?

In direction?

Up or down, what is the acceleration of the ball?

–9.8 m s–2

Remember:

air resistance is negligible

Describe the horizontal motion of this tennis ball.

Are there horizontal forces acting on the ball?

Does the horizontal velocity change?

Summarise your learning for a vertical projectile

Direction of motion

Forces Velocity Acceleration

Horizontal

Vertical

Summarise your learning for a vertical projectile

Direction of motion

Forces Velocity Acceleration

Horizontal

Air resistance negligible so no forces in the horizontal

Constant (in this case 0 m s–1)

None

VerticalAir resistance negligible so only force of gravity acting in the vertical

Changing with time

Constant or uniform acceleration of – 9.8 m s–2

Another projectile situation…

Picture a motorcyclist…

…on the top of a tall buildingabout to perform a death-defying stunt of incredible skill.

DON’T TRY THIS AT HOME

Predict her path once she launches off the building.

Predictions for a horizontal projectile

Direction of motion

Forces Velocity Acceleration

Horizontal

Vertical

Just as she launches…someone switches off gravity!

Predict her path with no gravity.

Remember: air resistance is negligible.

Switching gravity back on…

Virtual Higher Physics → Mechanics andProperties of Matter → Projectile Motion→ Video of projectile motion

(Motion Grapher Simulations:ball projected horizontally (horizontal component)ball projected horizontally (vertical component))

Summarise your learning for a horizontal projectile

Direction of motion

Forces Velocity Acceleration

Horizontal

Vertical

Summarise your learning for a horizontal projectile

Direction of motion

Forces Velocity Acceleration

Horizontal

Air resistance negligible so no forces in the horizontal

Constant None

VerticalAir resistance negligible so only force of gravity acting in the vertical

Changing with time

Constant or uniform acceleration of – 9.8 m s–2

Class challenge!

Can you save the motorcyclist from

being eaten?

http://www.absorblearning.com/media/attachment.action?quick=ww&att=2357

Do you believe in physics?Do you trust the equations of

motion?Would you jump over the crocodiles based on the

equations?

Verifying the equations of motion

How could you use the equipment to verify the

equations of motion?

Okay then…some hints

What determines the horizontal displacement?

What determines the time spent in the air?

What is the initial vertical velocity of a

horizontal projectile?

Class challenge

Use the equipment to determine the horizontal velocity with which the ball leaves the launcher.

Safety warnings

(c) Pasco Feedback

Class challenge

How well have you understood?

Calculate the horizontal velocity

required to save the motorcyclist from

being eaten.

http://www.absorblearning.com/media/attachment.action?quick=ww&att=2357

What formula can be used to calculate

the horizontal displacement of an object

fired horizontally if horizontal velocity

and time of flight are known?

sh = uht + ½at2 horizontal displacement (m)

horizontal velocity (m s–1)

time of flight (s)

What formula can be used to calculate

the vertical displacement of an object

fired horizontally?

sv = uvt + ½at2 vertical displacement (m)

initial vertical velocity (m s–1)

time of flight (s)

Which will hit the ground first?

Predict, observe, explain

Are the two balls identical?Does it matter?

A thought experiment: the frictionless marble on the

frictionless surface

The marble is travelling horizontally at 5 m s–1. Describe its motion at:

0.1 s, 0.2 s, 0.3 s, 0.4 s, 0.5 s, 0.6 s, 0.7 s, 0.8 s, 0.9 s, 1.0s

A thought experiment: the frictionless marble on the

frictionless surface

How can we calculate the horizontal displacement at:

0.1 s, 0.2 s, 0.3 s, 0.4 s, 0.5 s, 0.6 s, 0.7 s, 0.8 s, 0.9 s, 1.0s

The frictionless marble dropped off the Eiffel Tour (into the air-resistance-free Paris sky)

How can we calculate the vertical displacement at:

0.1 s, 0.2 s, 0.3 s, 0.4 s, 0.5 s, 0.6 s, 0.7 s, 0.8 s, 0.9 s, 1.0s

The frictionless marble:the complete picture

Using Excel, we can plot a graph of

horizontal displacement against vertical

displacement.

Observe and explain

Still don’t believe the independence of horizontal and

vertical components?

Two more possibilities…

A traditional method involving:

• five small cans, open at each end• (take care of sharp edges)• a white board with graph paper (traditional not • interactive)• a method of fixing cans to the board.• a ball• a good aim.

Position the cans so the ball, when projected horizontally, will fall through each can.

A higher technology method involving:

The photo shown above must have been faked. Explain!© Pasco Feedback

Group thinking

What do you already know that you can apply to projectiles fired at an angle?

Think forces, vectors, equations…

© PASCO Feedback

Hints!

Any vector can be

resolved into its

horizontal and vertical

components.

The horizontal component

launch velocity (m s–1 )

θ

cos

cos

component launch velocity cos

adjacent

hypotenuse

adjacent hypotenuse

horizontal

The vertical component

launch velocity (m s–1 )

θ

sin

sin

sin

opposite

hypotenuse

opposite hypotenuse

vertical component launch velocity

Calculate the launch velocity.

Using this, resolve the vectors and calculate the range of the projectile.

The range is how far the projectile travels horizontally.

© PASCO Feedback

From the measured range, calculated what the launch velocity should be.

Are the values the same?

Explain!

© PASCO Feedback

Predict, then determine experimentally and by calculation which angle will give the greatest range for a fixed launch velocity.

© PASCO

Summarise your learning for a projectile fired at an angle to the

horizontalDirection of motion

Forces Velocity Acceleration

Horizontal

Vertical

Direction of motion

Forces Velocity Acceleration

Horizontal

Air resistance negligible so no forces in the horizontal

Constant None

VerticalAir resistance negligible so only force of gravity acting in the vertical

Changing with time

Constant or uniform acceleration of – 9.8 m s–2

Summarise your learning for a projectile fired at an angle to the

horizontal

Summarise your learning for all projectiles!

Direction of motion

Forces Velocity Acceleration

Horizontal

Vertical

Projectiles at an angle to the horizontal

http://www.absorblearning.com/media/attachment.action?quick=wx&att=2359

Select a velocity and select an angle.

Calculate the horizontal and vertical components

Will the projectile hit the target?

Other resourceshttp://www.helpmyphysics.co.uk/projectile.htmlhttp://www.upscale.utoronto.ca/GeneralInterest/Harrison/Flash/ClassMechanics/Projectile/Projectile.swf

A thought experiment… remember our death-defying motorcyclist?

What would happen if the building were taller? And the horizontal velocity greater?

And if the Earth’s surface curved away more steeply?

This is what Newton thought about, sometime between 1643

and 1727.

http://www.smaphysics.ca/phys40s/field40s/newtmtn.html

This is taken inside an aircraft. Explain why these NASA trainee astronauts (class of 2004) appear weightless.

© NASA

Watch the clip on microgravityhttp://microgravityuniversity.jsc.nasa.gov/theProgram/video/video.cfm

© NASA

Group challenge!

Complete the Weightless Wonder task

to apply your understanding of

equations of motion to a real situation.

http://www.nasa.gov/audience/foreducators/topnav/materials/listbytype/Exploring_Space_Through_Algebra_Weightless_Wonder.html

© NASA

What is gravity?What is the force of gravity?

What are the effects of gravity?What do we know about gravity?How can we make use of gravity?

Investigating the force of gravity on Earth

Using classroom resources, investigate how

you could measure the gravitational field

strength on Earth.

What are you measuring?

How are you measuring it?

What does it mean?

© NASA

Uncertainties in your results

© NASA

What do the results mean?What have you measured?

© NASA

Can you measure gravitational field strength directly?

© NASA

Making use of the force of gravity

Newton’s thought experiment of 300 years ago

became a reality on 4 October 1957.

The Soviet Union (USSR) successfully

launched the world’s first artificial satellite,

Sputnik 1.

http://history.nasa.gov/sputnik/sputnik.wav

Researching physics

What was the significance of Sputnik’s launch,

more than 50 years ago?

What impact has the space race and our ability

to launch satellites into space had on life on

Earth?

Topics for researching

• The historical aspects of the space race and its significance to humankind.

• Low orbit and geostationary satellites.

• Satellite communication and surveying.

• Environmental monitoring of the conditions of the atmosphere.

Scientific communication andcriteria for assessment

Another opportunity to build skills for

researching physics units.

Insert more information once released!

Quality sources for research.

Communication of understanding, including

summarising information in own words.

Scientific content within communication.

Reviewing our learning

In this section, we have developed our

understanding of motion to build from vertical

projectiles, to horizontal projectiles and projectiles at

an angle.

We have followed the thought processes of Sir

Isaac Newton through to the very first successful

launch of a satellite, and considered how scientific

developments impact on life on Earth.

A final thought…This paragraph is taken from an article about a

sample of wood being taken on a NASA

mission to orbit Earth.

A piece of Sir Isaac Newton's apple tree will

‘defy’ gravity, the theory it inspired, when

it is carried into space on the next Nasa

shuttle mission. © BBC News website

Discuss!