Objective 5

MOTION & FORCES

Have this on your desk for EVERY question involving math.

FORMULAS

Constants & Conversions

Ruler

EVERY FORMULA YOU NEED IS ON THE CHART.You won’t ALWAYS use all the numbers given.Eliminate bad answers.ALWAYS use your calculator!!!!

• Average velocity (speed) is the change of position of an object over time. Velocity is a vector quantity that includes direction.

SPEED describes how fast an object moves.

Speed (v) = Distance Time

AccelerationChange in velocity over

change in time

a =final velocity – initial velocity

∆T

Acceleration

0

20

40

60

1 3 5 7 9 11 13 15

Time (sec)Ve

loci

ty ((

m/s

)(m)

(slope)

Units for acceleration m/s/s or m/s2

• A 2.4 km

• B 2.4 m

• C 23 cm

• D 24 mm

The speed of sound in human

tissue is about 1600 m/s. If an

ultrasound pulse takes 1.5 x 10-5s

to travel through a tissue, what is

the thickness of the tissue?

TIME

DISTANCESpeed = distance

time

1600m/s = distance

1.5 x 10-5 s

.024m = distance

The table above shows experimental data collected when four cars moved along a straight-line path. According to these data, which car moved with a constant acceleration of 2 m/s2 ?

A Car QB Car RC Car SD Car T

a =final velocity – initial velocity ∆T

You can immediately eliminate Q & R…WHY?

A(carS) = 4m/s-2m/s = 2m/s

2s-1s 1s

Use this method to check car S & car T.

Newton’s 1st Law of Motion

A body in motion will remain in motion.

A body at rest will remain at rest.

UNLESS there is a force acting on that object.

Newton’s 2nd Law of Motion

Force = mass x acceleration

Newton’s 3rd Law of Motion

For every action (force) there is an equal and opposite reaction (force).

Friction

A force that acts in a direction opposite to the motion of two surfaces in contact with each other.

MOMENTUM

• The effect of motion is momentum.

• Momentum = Mass x Velocity

Work• Work: amount of energy

transferred by a force

• W = F x d

• The work done by forces on an object = changes in energy for that object.

• Work and Energy are measured in Joules

• 1 Joule=1 Newton • meter

Machines use power

• Power: the rate at which energy is used (work is done)

• P=Work/time• Power is measured in

H.P. or watts• 1 watt = 1 Joule

1 sec

SIMPLE MACHINESmake WORK easier

3 Classes of LEVERS

(Resistance)

The human bicep muscle is a classic example of a third class lever. Similar analogies can be drawn from almost all joints in the human body.

•

% Efficiency• NO MACHINE IS 100%

efficient.

• Energy is lost as HEAT!!!

%efficiency = work output X 100 work input

WAVES

Velocity of a wave = frequency x wavelength(m/s) (Hz) (m)

ν = ƒ x

KINETIC ENERGY- energy of motion

KE= ½ (mass x velocity)2

GRAVITATIONAL POTENTIAL ENERGY

PE= mass x acceleration due x heightto gravity

ENERGY = mass x (speed of light)2

Current = Voltage / Resistance

Electrical Power = Voltage x Current

Electrical energy = power x time

Electricity – flow of electrical charge

Convection, Conduction, and Radiation

• Convection- Heat transfer by the mass movement of molecules

•

Convection, Conduction, and Radiation

• Conduction- Heat transfer by the collision of molecules that are in contact

Convection, Conduction, and Radiation

• Radiation- Heat transfer with no physical contact

Convection, Conduction, and Radiation

.

PRACTICE WITH YOUR FORMULA CHART

• EVERY FORMULA YOU NEED IS ON THE CHART.

• You won’t ALWAYS use all the numbers given.

• Eliminate bad answers.

• ALWAYS use your calculator!!!!

Density of an object is 1.25 g/ml at 20°C and the mass is 4 g, what is the

volume?

An object falling from the sky traveled

4000 m in 8 seconds, what is the

speed of the object?

A car accelerates from 0 m/s to 100 m/s in 5 seconds.

What is the acceleration of the

car?

A 0.75 kg ball is thrown with a velocity of 40 m/s,

what is the momentum of the ball?

A 25 kg rock is increasing in velocity from 0 m/s to 50 m/s

in 10 seconds. What is the rock’s force?

If a box is moved 5 m with a force of 100 N, how much work

is done?

How much power is the result of

completing 5000 J of work in 30 seconds?

What is the % efficiency of a

machine if the work output is 40 J and

the work input is 50 J?

What is the kinetic energy of a 100 kg object traveling a 5

m/s?

What is the potential energy of a 50 kg rock sitting on

top of a 75 m cliff?

What is the velocity of a wave with a

frequency of 1000 hz and a

wavelength of 0.00000045 m?