Physics 2a

If the two vectors are added together, which drawing shows the correct resultant vector? What is the magnitude of the resultant vector?

Option B in our case theta = 90 and cos90 = 0 => R = sqrt ( 4^2 + 3^2 ) => R = sqrt ( 25) => R = 5

A fox locates it's prey, usually a mouse, under the snow by the slight sounds that it makes, the fox then leaps straight into the air and burrows its nose into the snow when it lands, to catch its next meal. Which of the three pairs of velocity versus time, Vy(t) and acceleration versus time, ay(t) graphs represent the free-fall motion of the fox? Assume the +y direction is up.

Option: B

A person blood pressure is measured to be 117+- 5mm Hg. What is the percent uncertainty? What is the uncertainty in a blood pressure measurement of 81 mm Hg?

Percent uncertainty = 5/117 x100% = 4% uncertainty = 4.275 x 81/ 100= 3 mm Hg

time dimension

T

Prefix - "tera-" Symbol: ? Power: ?

T, 10^12

Given any two vectors...

The sum of two vectors cannot be perpendicular to both vectors

Rules of Significant Figures

Trailing zeros are significant only if decimal , leading zeros are never significant

A ball is thrown straight up. Which of the following is correct about the magnitudes of the balls velocity (v) and acceleration (a) at the highest point in its trajectory? V=/=0, but a=9.80m/s^2 V=0, but a=9.80m/s^2 There is not enough information to determine both v=0 and a=0 v=/=0, but a=0

V=0, but a=9.80m/s^2, because the velocity of a ball is zero at the top of its trajectory.

What is the velocity of the red car relative to the blue car?

Vx= vx - V Vx= 24 m/s - 36 m/s = -12 m/s

When t=1s, it's position is x= -2.0m, what is the position of the particle at t= 7.0s?

X(1s)= -2m = 1/2(1+3)2 - 1/2(3)(3)= 4m-4.5m= -0.5m =-2-0.5= -2.5m

At t=0 a ball, initially at rest, starts to roll down a ramp with constant acceleration. You notice it moves 4 feet between t=0 seconds and t=1 second. How far does it move between t=1 second and t=2 seconds?

X= xo + vot + 1/2at^2 (basic equation for finding position)

A busy chipmunk runs back and forth along a straight line of acorns that has been set out between its burrow and a nearby tree At some instant, it moves with a velocity of - 1.25 m/s . Then, 2.87 s later, it moves with a velocity of 1.93 m/s . What is the chipmunk's average acceleration during the 2.87 s time interval?

acceleration= vf-vi/t= 1.93- -1.25/2.87= 3.18/2.87= 1.11 m/s^2

A gnat takes off from one end of a pencil and flies around erratically for 32.6 seconds before landing on the other end of the same pencil. If the gnat flew a total distance of 7.15 meters, and the pencil is 0.0963 m long, find the gnat's average speed and the magnitude of the gnats average velocity.

average speed= total distance/time= 7.15/32.6= 0.219 m/s average velocity= displacement/time= 0.0963/32.6= 0.00295

Jack and Jill exercise in a 25.0-m-long swimming pool. Jack swims 9 lengths of the pool in 153.7 seconds (2 minutes and 33.7 seconds), while Jill, the faster swimmer, covers 10 lengths in the same time interval. Find the average velocity and average speed of each swimmer

average velocity= displacement/time Jacks velocity= 25/153.7= 0.162m/s Jacks average speed= 25*9/153.7= 1.46 m/s Jill's average velocity= 0/153.7= 0 m/s Jill's average speed= 25*10/153.7= 1.63 m/s

Prefix - "micro-" Symbol: ? Power: ?

back-words h, 10^-6

Prefix - "centi-" Symbol: ? Power: ?

c, 10^-2

A person is initially driving a car east down a straight road. The magnitude of the instantaneous acceleration is increasing with time and the direction the acceleration is always to the west. The speed of the car is...

decreasing but then increasing

average velocity formula

dimension= L (distance)/T (time)

You notice a one-dimensional-thinking snail crawling along one rail of a railroad track. Naturally, you remove it to a safer place. But before you do, you observe it as it moves from position xi = -98.7 cm to position xf = -63.5 cm along the rail, as measured from a nearby joint between two segments of rail. What is the magnitude of the snail's displacement, x in centimeters?

displacement= xf - xi= -63.5 - -98.7= 35.2cm

Which is not a vector? displacement distance instantaneous velocity acceleration average velocity

distance

Destiny is eating lunch at her favorite cafe when her friend Jada calls and says she wants to meet her. Jada is calling from a city 55 miles away and wants to meet Destiny somewhere between the two locations. Jada says she will start driving right away, but Destiny needs 10 min to finish her lunch before she can begin driving. Jada plans to drive at 60 mph, whereas Destiny usually averages about 80 mph. Ignore acceleration and assume the highway is a straight line. How many minutes tmeet will jada be driving before she meets destiny? How many miles d will destiny have traveled when they meet?

distance traveled by jada= 60t Time of drive by destiny= t-10min= t-.167 hour distance of travel by destiny= 80(t-.167) Total distance= 55 miles 60t + 80(t-.167)= 55 60t + 80t-13.36= 55 140t= 68.36 t= 0.488 hour= 29.28 minutes distance tracked by destiny = 80(t-0.167) 80(0.488-0.167)= 25.68 miles

Average speed=

distance/time

Prefix - "femto-" Symbol: ? Power: ?

f, 10^-15

Displacement=

final position - initial position

A squirrel runs along an overhead telephone wire that stretches from the top of one pole to the next. The creature is initially at position xi = 3.07 m, as measured from the center of the wire segment. It then undergoes a displacement of x = -6.53m. What is the squirrel's final position xf?

final position= displacement + initial= -6.53 + 3.07= -3.46

initial velocity=

final velocity - (acceleration x time)

average acceleration=

final velocity-initial velocity/time

A person is initially driving a car cast down a straight road. The magnitude of the instantaneous acceleration is decreasing with time, but the direction of the acceleration is always to the east.

increasing, since the car is accelerating towards East, the speed of the car increasing with time towards East

Prefix - "kilo-" Symbol: ? Power: ?

k, 10^3

What does mass=?

kg

SI base unit for mass

kilogram (kg)

Prefix - "milli-" Symbol: ? Power: ?

m, 10^-3

SI base unit for length

meter (m)

Prefix - "nano-" Symbol: ? Power: ?

n, 10^-9

Prefix - "pico-" Symbol: ? Power: ?

p, 10^-12

What does Time=?

s

SI base unit for time

second (s)

Average velocity=

total displacement/total time

An infants pulse rate is measured to be 129+or- 6 beats/min. What is the uncertainty in this measurement? What is the percent uncertainty?

uncertainty = 6 beats per minute Percent uncertainty= A/A x 100%= 6/129 x 100= 5

A cheetah can accelerate from rest to a speed of 28.0 m/s in 5.00s. What is its average acceleration a?

v1= 0 m/s vf= 28.0 m/s t= 5 s average acceleration= vf-vi/t= 28.0-0/5= 5.6 m/s^2

Formula for speed:

v= d/t, where v is speed, d is distance, t is time

When throwing a ball straight up, which of the following are correct about the magnitudes of its velocity v and its acceleration a at the highest point in its path?

v=0, but a=9.80 m/s2

Classify each quantity as a vector, a scalar, or cannot be determined. 6.86m 68.0 37.8 ft 13.2 m/s east

vector (magnitude and direction): 13.2 m/s east scalar (only magnitude): 6.86m, 68.0, 37.8 ft

A long jumper leaves the ground at an angle of 20.0o above the horizontal and at a speed of 11.0 m/s. (A) How far does he jump in the horizontal direction? (B) What is the maximum height reached?

(A) R= Vo^2sin2delta(0)/g , Vo= 11m/s, Delta(0)= 20 R= (11)^2 sin(40)/9.8m/s^2= 7.94m (B) h= vo^2sin^2delta(0)/2g= (11)^2sin^2(20)/2(9.8)= 0.722m

Which of the following symmetric trajectories has the "longest" time of flight, if all trajectories have the same initial speed ? vo? (A) 75 (B) 60 (C) 45 (D) 30 (E) 15

(A), because A has the highest height, in which will cause the longest time of flight.

A destroyer simultaneously fires two shells with the same initial speed at two different enemy ships. The shells follow the parabolic trajectories shown. Which ship gets hit first? (A) Enemy 1 (B) Enemy 2 (C) Both ships are hit about the same time

(B) enemy 2, because enemy 2 has the lowest maximum height, which will cause the ship to get hit first.

After an average acceleration of 3.49 m/s^2 during 2.25s, a car reaches a velocity of 16.5 m/s. Find the cars initial velocity.

(initial velocity= final velocity-(acceleration x time)) initial velocity= 16.5 m/s - (3.49 m/s^2 x 2.25)= 8.65 m/s

U.S. Customary System, and force (derived quantity)

1 lb = 0.454 kg, 1 lb= 32.17 ft/s2=4.448 N

Following the rule for significant figures and rounding, how should you express? 1.2586 - 1.11

1.2586 - 1.11 = 0.15

What is the order of magnitude of 7.2450 x 10^-3?

10 x 10^-3-> 1-3=-2

Write the name of the metric system prefix associated with each mathematical factor. 10^-6: 1/100: 0.001: 1000:

10^-6= micro 1/100= centi 0.001= milli 1000= kilo

What is Newton (N)?

1kg x m/s2 = 1N

Convert 98.6 m^2 to square centimeters

1m = 100cm (1m)^2=(100cm)^2 1m^2=1x10^4 cm^2 98.6m^2 x 1x10^4cm^2/1m^2= 9.86 x 10^5

Write numbers in scientific notation: 291.7 0.0960

2.917 x 10^2 9.60x10^-2

Convert 3.38 km to centimeters

3.38km x 1000m/1km x 100cm/1m= 3.38 x 10^5

64.5 Mm= ? km (conversion)

64.5 Mm x ? Km/ 1 Mm Prefixes : Mm - Km= 6 - 3= 3 64.5Mm x 10^3km/1 Mm= 6.45 x 10^4

What does distance=?

= m

An object experiences a constant acceleration A—> and attains a velocity Vf—> as shown in the figure. Which of the vectors could be an initial velocity of the object? Assume the magnitude of the y-component of each vector equals the y-component of Vf—>.

A, because acceleration is negative and constant and final velocity is positive so initial velocity should also be positive and same direction.

What are the objectives of physics?

Find the fundamental laws that govern natural phenomena, develop theories and models that can "predict" the behavior of natural world around us, express laws in the language of mathematics to quantify physical properties

The speed of propagation of the action potential (an electrical signal) in a nerve cell depends (inversely) on the diameter of the axon (nerve fiber). If the nerve cell connecting the spinal cord to your feet is 1.3 m long, and the nerve impulse speed is 17 m/s, how long does it take for the nerve signal to travel this distance?

Formula for speed (v=d/t, but trying to find time, so t= d/v) t= d/v= 1.3m/ 17 m/s= 0.076s

Why do we study physics?

Fundamental of all sciences, explain phenomena in the universe, develop fundamental concepts and models for natural behavior, foundation of other physical scienes

The quantities that do not depend on any other physical quantity for their measurement are known as___.

Fundamental quantities

Prefix - "giga-" Symbol: ? Power: ?

G, 10^9

The figure graphs the x-component of the velocity of a car traveling in a straight line. Over which intervals of time is the car slowing down?

Intervals 2 and 6

Distance dimension

L

What are the three most used fundamental quantities?

Length (L), Mass (M), Time (t)

mass dimension

M

Prefix - "mega-" Symbol: ? Power: ?

M, 10^6

Five students are asked to draw a motion diagram for a baseball falling downward after being released from rest. Each student draws a different diagram. Which students diagram correctly represents the motion of the falling ball?

Anne because the ball will increase in speed with time.

An object that is slowing down has a speed that is___.

Approaching zero

Two vectors are shown in the figure. The x-direction is horizontal, the y direction is vertical, and each grid square represents one unit. The components of the resultant vector C= A + B are...

Ax = -4 Ay = 6 Bx= 3 By= -1 Cx= Ax + Bx= -4 + 3 = -1 Cy= Ay + By= 6 + -1 = 5 C = Cx + Cy= -1 + 5= 4 The components of C=A + B are -1 and 5

What is the maximum pull you can apply to the 1 kg block without breaking the string when the maximum tension in the string is 6 N?

Block 2: 6N= (2kg)= 3m/s^2 Block 1: Fpull- 6N= (1kg)(3m/s^2) Fpull= 9N

Realms of physics (divided into six major areas)

Classical mechanics, electromagnetism, thermodynamics, optics, quantum mechanics, astronomy & relatively

The volume of a sphere is given by the equation V=4/3 pi r^3, where r is the radius. Calculate the volume of a sphere with a radius of 429 pm in cubic meters.

Convert picometers to cubic meters (1m= 1x10^12 pm) 429pm x 1m/1 x10^12pm= 4.2900x10^4 V= 4/3pi (4.29x10^4)^3=

At which lettered point is the object moving the fastest?

D

What is the correct prefix for 0.0000007s?

D