Objective 5 Motion, Forces, and Energy

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# Objective 5 Motion, Forces, and Energy - PowerPoint PPT Presentation

Objective 5 Motion, Forces, and Energy. IPC 4A – Calculate speed, momentum, acceleration, work, and power in systems such as in the human body, moving toys, and machines. Common measurements and symbols. Using the formula chart. 1. Circle what you are asked to find

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### IPC 4A – Calculate speed, momentum, acceleration, work, and power in systems such as in the human body, moving toys, and machines.

Using the formula chart

1. Circle what you are asked to find

2. Underline given facts with numbers and units and write the symbol above it.

3. Identify the formula(s) you will use from the formula chart

4. Rearrange the formula for what you’re asked to find.

5. Put in numbers for symbols and solve.

Rearranging formulas

When a formula is not solved for the variable you are trying to find, then you need to rearrange it until your variable is alone on one side of the equation.

d

v

t

Rearranging formulas

Example, the speed formula is:

If you are given speed and time and want to find distance, what would the formula be?

d

v

t

d

t

t

x

v

x

d

v

x

t

t

Rearranging formulas

Here, you divided d by t. To move t to the other side, do the opposite, multiply by it.

t cancels on the right side

And you are left with the formula for d.

Speed and Velocity

How fast an object is traveling.

Velocity has direction, speed does not.

Acceleration

The change in velocity

If an object is moving at a constant speed, acceleration = 0

Negative acceleration (deceleration) means the object is slowing down.

Work

Using force to move an object a certain distance.

If there is no movement, there is no work done. If distance = 0, work = 0

Does not depend on the time it takes to do the work

If Distance = 0,

then

Work = 0.

Power

The rate at which work is done.

More power means the same work can be done faster.

What is the power of this motor?

Power = Work/time

Time = 5 s

We must find the work first!

Work = Force x distance

= 10 N x 2m = 20 J

Power = Work/time

= 20J/5s

=4 Watts

Momentum

The product of an object’s mass and velocity.

Can be thought of as how difficult it is to stop a moving object.

A stopped object has zero momentum.

Conservation of Momentum

In collisions, total momentum does not change. The momentum of the objects (together) before the collision is the same as the momentum of the objects (together) after the collision.

Distance vs. Time graphs
• In a distance vs. time graph, the slope of the line is the speed of the object.
• If you have a horizontal line, the object is stopped.
Constant speed away from a point

Constant speed toward a point

The line gets less steep – slowing down

The line gets steeper – speeding up

Velocity vs. Time Graphs
• In a velocity vs. time graph, the slope of the line is the acceleration of the object.
• In this type of graph, a horizontal line means that the object is moving at a constant speed.
Two ice hockey players are skating directly at each other. The first has a mass of 87 kg and is skating at a constant speed of 2.6 m/s. The second skater has a mass of 78 kg. How fast must the second skater be skating in order to have a momentum similar to the first skater?

A 2.3 m/s

B 2.9 m/s

C 3.4 m/s

D 5.2 m/s

How much force is needed to accelerate a 1,300 kg car at a rate of 1.5 m/s2?

F 867 N

G 1,950 N

H 8,493 N

J 16,562 N

An ant crawled from Point A to Point B in 4.0 seconds. To the nearest tenth, what was the ant’s speed in centimeters per second?

Assume the ant traveled 5.6 cm.

1.4 cm/s

The diagram represents the total travel of a teacher on a Saturday. Which part of the trip is made at the greatest average speed?

F Q

G R

H S

J T

A car traveled 150 km in 2.5 hours. What was its average speed in km per hour? Record and bubble in your answer on the answer document.

60 km/h

Which bike rider has the greatest momentum?

A A 40 kg person riding at 45 km/h

B A 50 kg person riding at 35 km/h

C A 60 kg person riding at 25 km/h

D A 70 kg person riding at 15 km/h

IPC 4B – Investigate and describe [applications of] Newton’s laws such as in vehicle restraints, sports activities, geological processes, and satellite orbits.
Forces
• Force can be defined as a push or a pull.
• Forces can be balanced, which mean they are equal and opposite with no change in direction. If the forces on an object are balanced, it will either remain at rest or it will move at a constant speed in a straight line.

### Unbalanced forces cause an object to accelerate (speed up, slow down or change direction) in the direction of the largest force.

Newton’s Laws

Newton’s First Law: An object at rest will remain at rest and an object in motion will remain in motion at a constant velocity unless acted upon by an unbalanced force.

• The Law of Inertia.
Newton’s Second Law:
• Force = mass x acceleration
• For a constant force, if mass increases acceleration decreases
• For a constant mass, if force increases, acceleration increases

F = ma

The ball’s mass is lower, so its acceleration is higher.

The cannon’s mass is greater, so its acceleration is lower.

### Newton’s Third Law: For every action force, there is an equal and opposite reaction force.

In the event of an accident, air bags and seat belts may help reduce injury to a passenger by decreasing the force that stops the passenger’s motion. The force is reduced because the seat belts or air bags decrease the —

A mass of the passenger

B acceleration of the passenger

C reaction time of the driver

D speed of the vehicle

The illustration above shows a student about to throw a ball while standing on a skateboard. Which illustration below correctly shows the skateboard’s direction of motion after the student releases the ball?
The table shows times required for the same toy car to travel 10 m across an identical section of a floor after it is pushed. The difference in times was probably caused by differences in —

A force exerted

B surface friction

C air resistance

D car mass

IPC 5A – Demonstrate wave types and their characteristics through a variety of activities such as modeling with ropes and coils, activating tuning forks, and interpreting data on seismic waves.
Types of Waves

1. Transverse

### Calculating Wave Speed

Velocity of a wave = Wavelength • Frequency

Measured in Hz

A surfer wishing to ride a big wave is most

interested in a wave’s —

A rarefaction

B compression

C amplitude

D wavelength

At 0°C sound travels through air at a speed of 330 m/s. If a sound wave is produced with a wavelength of 0.10 m, what is the wave’s frequency?

F 0.0033 Hz

G 33 Hz

H 330 Hz

J 3300 Hz

### IPC 6A – Describe the law of conservation of energy.

Energy
• energy- the ability to do work
• unit: joule (J)
Types of Energy:
• kinetic energy- the energy of motion
• the faster an object moves, the more kinetic energy it has
• depends on both mass & velocity
• KE = ½ (mv2)
• potential energy- energy of position
• stored energy that the object was given when work was done on it – a ball rolled to the top of a hill
• it has the ability to give that work back—a stretched rubber band
• GPE is potential energy due to gravity. GPE = mgh (remember g = 9.8m/s2)
law of conservation of energy-
• energy may neither be created nor destroyed
• it can only be transformed into various forms—from kinetic to potential, from chemical to mechanical
• the total energy in the system is constant
maximum potential

maximum potential

maximum kinetic

Where is the PE greatest?Where is the PE least?Where is the KE greatest?Where is the roller coaster moving the fastest?
Types of Energy

mechanical energy- energy of motion—hitting a ball, walking, blood flowing through your vessels

heat energy- internal motion of atoms; usually results from friction—causes phase & temperature changes

chemical energy- energy that exists in the bonds that hold atoms together—starting a fire, burning fuel, digesting food

nuclear energy- energy associated with the nucleus of an atom; produces the sun’s energy due to nuclear fusion--hydrogen changes to helium

electromagnetic energy- energy associated with moving charges—microwaves, X-rays

Powerful Plankton

The U.S. Naval Research Laboratory has created an experimental marine fuel cell that could produce enough electricity to power ocean-monitoring devices. This fuel cell runs on seawater and sediment, with the help of plankton. Some plankton on the surface of ocean sediments use dissolved oxygen to break down organic matter, releasing energy; this is an aerobic process. The plankton in the deeper sediments break down organic matter without using oxygen; this is an anaerobic process. These two processes create a difference in voltage between the surface of the sediment and the sediment farther down in the seabed. The voltage difference can be used to produce electricity-up to 5.0 x 10–2 watts of power. Energy supplied by this type of fuel cell can be obtained as long as there is organic matter in the sediment. Fuel cells powered by plankton from the seabed can be used to operate instruments that monitor ocean currents and water temperature. These fuel cells get their energy by converting —

F chemical energy to electrical energy

G electrical energy to mechanical energy

H hydroelectric energy to geothermal energy

J mechanical energy to chemical energy

### IPC 6B – Investigate and demonstrate the movement of heat through solids, liquids, and gases by convection, conduction and radiation.

Kinetic theory
• all matter is made up of atoms & molecules that act like tiny particles
• these tiny particles are always in motion; the higher the temperature, the faster the particles move
• at the same temperature, more massive (heavier) particles move slower than less massive (lighter) particles
• cold- the absence of heat
• heat transfer- the movement of heat from a warmer object to a cooler one
3 methods of heat transfer

1. conduction- heat is transferred through a substance, or by the direct contact of molecules

• takes place in solids, liquids, & gases, but does best in solids
• one particle must contact another for this to occur. In solids, the particles are close to each other, which makes contact easier.
Conductors vs. Insulators

conductors- substances that conduct heat better & more rapidly than others (silver, copper, iron)

insulators- substances that do not conduct heat easily (glass, plastic, wood, rubber)—wearing several layers of clothing in extremely cold weather

3 Methods of Heat Transfer

2. convection- takes place in liquids & gases as up-and-down movements called convection currents.

• Does not occur in solids
3 Methods of Heat Transfer

3. radiation- heat energy transfer through empty space

• This is how the sun heats the earth
Mud at the bottom of a fishpond has a temperature of 15°C. After a week of colder air

temperatures, the mud temperature drops to 12°C. Which of the following methods of heat transfer is most responsible for the change in the mud temperature?

A Water convection

B Air conduction

C Water reflection

A reflection

B conduction

D convection

A man who was sleeping wakes up because he hears the smoke alarm go off in his house. Before opening the bedroom door, the man feels the door to see whether it is warm. He is assuming that heat would be transferred through the door by —

A conduction

B convection

D compression

### Electric Circuits

IPC 6F – Investigate and compare series and parallel circuits. (10th grade only)

Circuits

To have an electric circuit, you need:

• a closed conducting path which extends from the positive terminal to the negative terminal.
• An energy source, such as a battery.
Series circuit
• each device is connected in a manner such that there is only one pathway by which charge can traverse the external circuit.

What happens if the first light bulb burns out?

Parallel Circuits
• In a parallel circuit, each device is placed in its own separate branch. The presence of branch lines means that there are multiple pathways by which charge can flow through the external circuit.

What happens if the first light bulb burns out?

Circuits Math

Voltage (Volts)

Current (Amps)

Resistance (Ώ)

F Q

G R

H S

J T

What is the current in a copper wire that has a resistance of 2 ohms and is connected to a 9-volt electrical source?

F 0.22 amp

G 4.5 amps

H 11.0 amps

J 18.0 amps

Which circuit is built so that if one lightbulb goes out, the other three lightbulbs will continue to glow?