Speed, Acceleration, and Momentum

page 10 & 11.

Essential Question: Explain if we lost all our time keeping devices, how would you keep up with where you are suppose to be and when to be there?

a measure of how fast you are going

t

ds

meters per sec (m/s)

t

ds

t

dv

Speed is a single measurement that tells how fast you are going.

Velocity is your speed and the direction you are going

Position means where something is compared with where it startedIf you are 7 km north of

school this is your position. If you walk back to the school, your position is zero (+7-7=0) even though you walked 14 km. (7km away plus 7 km back).

Distance is a length

Position vs time graph

The position vs time graph shows where things are at different times

Speed is the slope of the position vs time graph

Acceleration

Student Expectation:

The student is expected to calculate speed, momentum, acceleration, work, and power in systems such as in the human body, moving toys, and machines.

rate at which speed changesRate of change means the ratio of the amount of change divided by how much time it took to change

What is acceleration?

Units of cm/sec2 or m/sec2

vf – vi

t

2nd velocity 1st velocity

time

2nd velocity

Positive acceleration

Negative acceleration (or deceleration)

Zero acceleration

Acceleration is the slope of the speed vs. time graph

DON’T WRITE

MOMENTUM

Student Expectation:

The student is expected to calculate speed, momentum, acceleration, work, and power in systems such as in the human body, moving toys, and machines.

Momentum??? The sports announcer

says "Going into the all-star

break, the Texas Rangers have the momentum.

" The headlines declare “Dallas Mavericks are Gaining Momentum."

The coach pumps up his team at half-time, saying "You have the momentum; the critical need is that you use that momentum and bury them in this third quarter."

Momentum is a commonly used term in sports. A team that has the momentum is on the move and is going to take some effort to stop. A team that has a lot of momentum is really on the move and is going to be hard to stop. Momentum is a physics term; it refers to the quantity of motion that an object has. A sports team which is on the move has the momentum. If an object is in motion (on the move) then it has momentum.

Mass in motion

p = m v

kg m/s

What is momentum?

Formula

Units

Momentum

Mass (g)

Velocity (m/s)

Mass, speed, and momentum have a direct relationship!

Mass

Speed

Momentum

Mass

Speed

Momentum

If you increase the mass or the speed of an object, you increase its momentum.

states that the total momentum of a system can not change.

That means that the momentum of the system prior an action must equal the momentum after the action.

Positive and negative signs are used to tell the direction of the motion. That means momentum can be positive (moving to the right) or negative (moving to the left)

Before you throw the ball, your and the ball’s momentum is zero. In order for conservation of momentum to be true, after you throw the ball the total momentum must be zero.

m1v1=m2v2

(1 kg)(-20 m/s) + (40kg)(0.5m/s) = 0

What time is it… SUMMARY TIME!

YOU HAVE 3 MINUTES TO SUMMARIZE AT LEAST 5 THINGS YOU LEARNED

TODAY. MAKE SURE YOU WRITE IN COMPLETE

SENTENCES.

What time is it… SUMMARY TIME!

YOU HAVE 2 MINUTES TO SUMMARIZE AT LEAST 5 THINGS YOU LEARNED

TODAY. MAKE SURE YOU WRITE IN COMPLETE

SENTENCES.

What time is it… SUMMARY TIME!

YOU HAVE 1 MINUTE TO SUMMARIZE AT LEAST 5 THINGS YOU LEARNED

TODAY. MAKE SURE YOU WRITE IN COMPLETE

SENTENCES.