chapter 1. branches of physics measuring = units mass [kg] length/distance [m] time [s]

Chapter 1

Branches of Physics

Measuring = units

MASS [kg]

LENGTH/DISTANCE [m]

TIME [s]

What do these have in common?

Odd one out???

LBS vs. KGWeight is measured in pounds

(USA)

Mass is measured in kilograms

1 kg = 2.20462262 pounds

1 kg = 2.2 lbs

1 lb = 454 g

MASS

50 – 75 kg

MASS

Bumblebee bat – 1.5g – 2.0 g

MASS

Blue whales:Newborn –2.5 tonsAvg. 100 – 120 tonsBiggest – 190 tons

CONVERT

1) your weight in lbs to mass in kg (1 kg = 2.2 lbs)

2) 190 tons to pounds

1 mile = 1.609344 kilometers

1 mile = 1.6 km

1 yard = 0.9144 m

1 foot = 0.3408 m

1m = 3.2808 ft

Football field in meters?What is the length of a football field in meters?

120 yards

1 yard = 0.9144 m

mph – km / h – m/s

65 mph = 104 km/h

104 km / h to m/s

104 km = 140,000 m; 1 h = 3600 s

65 mph = 29m/s

km / h – m/s

75 km/h = 25 m/s =

120 km/h = 12 m/s =

Scale of the Universe A super cool applet

SN you need to remember:

Convert, use Scientific Notation

Examples

Examples

Examples

Examples

Practice 12.5 days to seconds ________________________________________

3.5 km to mm ______________________________________________

43 cm to km _______________________________________________

22 mg to kg _______________________________________________

671 kg to µg _______________________________________________

8.76 x 107 mW to GW _______________________________________

1.753 x 10-13 s to ps _________________________________________

Practice

The mass of the parasitic wasp Caraphractus cintus can be as small as 5x10-6 kg. What is the mass in a)g b)mgc) µg

PRACTICE2 dm - … mm2h 10 min - … s16 g - … micrograms0.75 km - … cm0.675 mg - …g462 µm - … cm35 km/h - … m/s

Precision & Sig. Dig.

LAB on Precision 1) Use the solid 1 m stick and measure the length of

the lab table

2) Use the 1 m stick marked with dm

3) Use the 1 m stick marked with cm

4) Use the actual meter stick to measure the length of your desk.

Write down the results to the maximum precision in each case.

SIG FIGS MADE SIMPLE

Pacifi

cP

resen

t Atla

ntic

Ab

sen

t1.450

14502500

0250.00

Sig. Fig.

100 000 100. 00

202 000 0.0050

340 505 0.00505

How many Sig.Figs?300 000 000 m/s

3.00 ×108 m/s

25.030 °C

0.006 070°C

1.004 J

1.305 20 MHz

PracticeThe value of the speed of light is

now known to be 2.997 924 58 ×108m/s.Express the speed of light in the following ways:

a) 3 SF

b) 5 SF

c) 7 SF

Adding and Subtracting# of digits 0.______ (after the

decimal point) = the least precise

3345.28 + 0.2 = 3345.48 = 3345.5

57.8 – 0.567 = 52.233 = 52.2

Multiplying and Dividing#SF (result) = the least #SF

(A*B)

1.34 x 2300 = 3082 = 3.1103

#SF (result) = the least #SF (A/B)

23967 / 45 = 532.6 =5.3102

Practice Bicyclists in the Tour de France reach speeds of 34.0 miles per hour (mi/h) on flat sections of the road. What is this speed in a) km/h and b) m/s - ?

1 mile = 1.61 km

Practice

a) find the sum of 756 g,

37.2 g, 0.83 g, and 2.5 g

b) the quotient 3.2 m/ 3.563 s

c) the product of 5.67 mm ×π

d) 27.54 s - 3.8 s

Density lab

Trig Review

Physics Quantities

SCALARS – magnitude

only

VECTORS –magnitude

anddirection

Vector vs. ScalarVelocity vs. Speed

Displacement vs. Distance

v – scalar; v – vector; (typed text)

a) b) c) d)

Comparing vectors

Which vectors have the same magnitude?

Which vectors have the same direction?

Which arrows, if any, represent the same vector?

Adding vectors

Subtracting vectors (+ negative)

Subtracting vectors (“fork”)

Check your understanding

Construct and label a diagram that shows the vector sum 2A + B. Construct and label a second diagram that shows B + 2A.

Construct and label a diagram that shows the vector sum A – B/2. Construct and label a second diagram that shows B/2 - A.

Adding vectors

Practice (p. 24, #24)

Vector A has a magnitude of 63 units and points due west, while vector B has the same magnitude and points due south. Find the magnitude and direction of

(a) A+B and

(b) A-B .

Specify the directions relative to due west.

Practice (p. 24, #25)

(a) Two workers are trying to move a heavy crate. One pushes on the crate with a force A , which has a magnitude of 445 newtons and is directed due west. The other pushes with a force B, which has a magnitude of 325 newtons and is directed due north. What are the magnitude and direction of the resultant force A+B applied to the crate?

(b) Suppose that the second worker applies a force - B instead of . What then are the magnitude and direction of the resultant force A-B applied to the crate?

In both cases express the direction relative to due west.

Adding vectors that are not

To add vectors that are not perpendicular to each other, we will use components.

Each vector has vertical and horizontal components, for example a has ax and ay

Components

Adding vectors

To find the resultant…

We need the components

Finding Rx and Ry

To find the resultant…

Direction?