ANSWERS PHYSICS INTRO:

 

MEASUREMENT: READ 1-1l, 1-2

 

Sec Review 1-4 Page 19

 

1) Which SI units would you use for the following measurements?

            A) the length of a swimming pool meters

            B) the mass of the water in the pool kilograms

            C) the time it takes a swimmer to swim a lap seconds

 

2) Convert the following measurements as indicated.

            A) 6.20 mg to kg         6.2mg is 6 places from kg so 0.0000062 kg

                        OR: Factor Label Method:

                                    6.2mg * 1 g                * 1kg = 6.2 * 10-6 kg

                                                1000 mg        1000g

            B) 3 * 10-9 sec to ms

3 * 10-9 sec * 1000 ms = 3 * 10-6 sec

                        1 sec

            C) 88.0 km to mm

88 km * 1000m * 1000mm = 88, 000, 000 mm = 8.8 * 107 mm

            1 km 1m

 

3) The following students measure the density of a piece of lead three times. The real density of lead is actually 11.34 g/cm3. Considering all the results, which person’s results were accurate? Which were precise? Were any both accurate and precise?

            A) Rachel: 11.32 g/cm3., 11.35 g/cm3., 11.33 g/cm3. Accurate AND Precise

            B) Danaiel: 11.43 g/cm3., 11.44 g/cm3., 11.42 g/cm3. Precise

            C) Leah: 11.55 g/cm3., 11.34 g/cm3., 11.04 g/cm3. Neither

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Math TEST:

 

ALL:

solve for x:      Y = Gm/x + r

METHOD 1:

                        Y-r = Gm/x +r –r

                        (Y-r) = Gm/x

                        x* (Y-r) = Gm/x * x

                        x(Y-r) = Gm

                        1/(Y-r)* x(Y-r) = Gm * 1/(Y-r)

                        x = Gm/ (Y-r)

METHOD 2:

                        Y-r = Gm/x +r –r

                        (Y-r) = Gm/x

                        1/Gm* (Y-r) = Gm/x * 1/Gm

                        (Y-r)/Gm = 1/x FLIPà

                        Gm/ (Y-r)=x

METHOD 3:

                        x*(Y = Gm/x +r)

                        x*Y = Gm +rx

                        x*(Y)-rx = Gm

                        x*(Y-r) = Gm

1/(Y-r)* x(Y-r) = Gm * 1/(Y-r)

                        x = Gm/ (Y-r)

 

 

 

the shape of a quadratic relationship(E parabola)                     a) y = 1/x

 

the equation of a linear relationship (C line)                     b. straight line

 

the shape of the graph of a constant increase  (B line)     c) y = mx + b

 

the equation of a quadratic relationship          (D parabola)      d. y = ax 2 + bx + c

 

                           e)

 

If a is acceleration (m/s2), v is change in position over time (m/s), x is change in position (m), and t is the time interval (s), which equation is dimensionally correct?

a) t = x/a              b) t = v2/x             c) v = a/t             d) t2 = x/a

 

s = m / (m/s2)              s = (m/s)2/m                m/s = (m/s2)/s              s2 = m / (m/s2)

s= m* s2 /m                 s= m2/s2/m                   m/s = (m/s2)*1/s          s2 = m* s2/m

s = s2 NO                    s= m/s2 NO                 m/s = m/s3 NO                        s2 = s2 YES

 

 


HONORS:

 

 

Plot these points and find a best curve fit:

 

X         Y

2          11

3          16

6          26

8          35

10        43.5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Solve these equations for T (T not zero)

 

D= VT + ½ A T        A= -V/T         V2 = - 2AD                 A=10

 

D= VT + ½ (10)T     10 = -V/T      V2 = -2 (10) D

                                    V = - 10T       D = V2 /(-20)

 

V2/(-20) = VT +5T

 

(-10T)2/(-20) = (-10T)T + 5T

 

100T2/(-20) = (-10T)T + 5T

 

-5T2 = -10T2 + 5T

0 = -5T2 + 5T

 

0 = 5T (-1T +1)

T- 0, 1