Momentum and Impulse

Momentum

→Inertia in motion→

p = m v

m = mass (kg)

v = velocity (m/s)

p = momentum (kg•m/s)

Momentum and inertia are not the same thing

Momentum only deals with objects in motion!

If the roller skate moves at 10 m/s,

and a mac truck is not moving

which has the greater momentum?

Mack truck: 0 = m x 0

P = mvRoller skate:

Momentum

https://www.youtube.com/watch?v=7zXjweYe358

Mass in Motion

Momentum is a vector quantity, magnitude and

direction

+ and - vectors are in opposite

direction

1. The momentum of an object depends upon the object's ________. Pick two quantities.a. mass - how much stuff it hasb. acceleration - the rate at which the stuff changes its velocityc. weight - the force by which gravity attracts the stuff to Earthd. velocity - how fast and in what direction it's stuff is movinge. position - where the stuff is at

2. Momentum is a ____________ quantity.a. scalar b. vector

3. Which are complete descriptions of the momentum of an object? Circle all that apply.a. 2.0 kg/s b. 7.2 kg•m/s, right c. 6.1 kg•m/s2, downd. 4.2 m/s, east e. 1.9 kg•m/s, west f. 2.3 kg•m/s

Momentum has a direct relationship

between velocity and mass

Double v = double p

Double m = double p

1/2 the v = half the p

1/2 the m = half the p

2X m and 2x v = 4x p

What has more momentum a smart car going 60 mph or a truck going 60 mph

• The big truck of course it has more mass!!!

Momentum will be large if -

either mass or velocity is large.

P = mv

Why do massive oil

tankers turn off their

engines 15 miles from

port?

They have so much momentum it takes a very, very long time to stop

4. The two quantities needed to calculate an object's momentum are __________ and ___________.

5. Consider the mass and velocity values of Objects A and B below.

Compared to Object B, Object A has ____ momentum.

a. two times the b. four times the

c. eight times the d. the same

e. one-half the f. one-fourth the

g. ... impossible to tell without knowledge of the F and a.

Momentum

EX. What is the momentum of a 3.5 kg

medicine ball traveling 4.3 m/s?

p = m v

3.5 kg (4.3 m/s)

= 15 kg•m/s

7.With what velocity must a 0.53-kg softball be moving to equal the momentum of a 0.31-kg baseball moving at 21 m/s?

6. Calculate the momentum value of ... . (Include appropriate units on your answers.)a. ... a 2.0-kg brick moving through the air at 12 m/s.

b. ... a 3.5-kg wagon moving along the sidewalk at 1.2 m/s.

Momentum

https://www.youtube.com/watch?v=7zXjweYe358

Mass in Motion

Review

Impulse

In order to change the momentum of an object, an external force must act on it.

J = ΔP ΔP = mΔv

J = F t ΔP = F t

therefore, F t = mΔv

A force at a

moment in time.

(vector quantity)

Example of Impulse (J)

As a cyclist rides down a hill, what happens to momentum?WHY?

Velocity must be changing…This means it has….ACCELERATION!What causes an acceleration?FORCE!

Conclusion: Forces cause a change in momentum