Physics Final
A car travels with an average speed of 22 m/s. What is this speed in km/s? In km/h?
(22 m/s) * (.001 km/m)= .022 km/s (.022 km/s) * (3600 s/h)= 79.2 km/h
A common speed limit in Vancouver, British Columbia, is 80 km/hr. If you are going 55 MPH, are you speeding? Show by converting 55 MPH to km/hr using the conversion factors on the inside front cover.
(55 miles/ 1 hour) *(1 hour/ 1 mile) *(1.609 km/hr) = 88.495 km/hr 88.495 km/hr > 80 km/hr, so I would be speeding
Staring from rest and moving in a straight line, a runner achieves a velocity of 7 m/s in a time of 2 seconds. What is the average acceleration of the runner?
(7 m/s)/ (2 sec)= 3.5 m/s^2
A runner moving with an initial velocity of 4 m/s slows down at a constant rate of 1.5 m/s^2 over a period of 2 seconds. What is her velocity at the end of this time?
1 m/s V= (4 m/s) + (1.5 m/s^2)*2
The velocity vs. time graph of an object curves. Is the acceleration of the object constant?
No, acceleration is not constant because the distance traveled changes as time goes on, thus making the velocity inconsistent, and by turn, causing the acceleration to also be inconsistent
A car traveling with constant speed rounds a curve in the highway. Is the acceleration of the car equal to zero in this situation?
No, because acceraltion is equal to the change in velocity over a given time and because the direction of the car is changing, the velocity is changing thus, causing the acceleration to also change and not equal zero
A ball attached to a string is whirled in a horizontal circle such that it moves with constant speed. Is the acceleration of the ball equal to zero?
No, because the ball is spinning, therefore there is acceleration
A car moves along a straight section of the road so that its velocity varies with time. Does the car ever go backwards?
No, because the velocity never goes backwards
A dropped ball gains speed as it falls. Can the velocity of the ball be constant in this process?
No, because velocity is equal to change in speed over a given period of time. Therefore, the speed changing would intern change the velocity.
What are the primary advantages of the metric system of units over the older English system of units?
The main advantage is its use of standard prefixes to represent multiples of 10 It also eliminates the complicated unit conversions such as miles, feet, yards, inches, etc
What units would have an appropriate size for measuring the rate at which fingernails grow? Explain.
The units mm/ month would be appropriate given that fingernails grow at a very slow rate
Starting from rest, a car accelerates at a constant rate of 3 m/s^2 for a time of 5 seconds. Compute the velocity of the car at 1 sec, 2 sec, 3 sec, 4 sec, and 5 sec and plot these velocity values against time.
V= 0 + (3 m/s^2)*(x sec)= 1 sec= 3 m/s 2 sec= 6 m/s 3 sec= 9 m/s 4 sec= 12 m/s 5 sec= 15 m/s *graph is a straight line upwards with velocity (m/s) vs. time (sec)
A car moves along a straight section of the road so that its velocity varies with time. At what point on a graph is acceleration the greatest?
Where the slope is the steepest
Staring from rest, a car accelerates at a rate of 4.2 m/s^2 for a time of 5 seconds. What is its velocity at the end of this time?
21 m/s V= 0 + (4.2 m/s^2)* 5
a book is 240 mm in width. What is the width in centimeters? In meters?
240 mm *(1 meter/1000 mm) * (100 cm/ 1 meter)= 24 cm 240 *(1 meter/1000 mm)= .24 meters
The volume of a cube is found by multiplying length x width x height. If an object has a volume of 2m^3, what is the volume in cubic centimeter? Remember to multiply each side by the conversion factor.
2m^3 *(1,000,000 cm^3/ 1 m^3)= 2,000,000 cm^3
A woman walks a distance of 360 m with an average speed of 1.2 m/s. What time was required to walk this distance?
300 seconds 1.2 miles/ sec = 360 miles/ x sec
A runner moving with an initial velocity of 4 m/s slows down at a constant rate of 1.5 m/s^2 over a period of 2 seconds. What distance does she travel during this process?
5 m d= v0t + 1/2at^2= (4 m/s)(2 s) + 1/2(-1.5 m/s^2)(4 s^2)
A runner traveling with an initial velocity of 2 m/s accelerates at a constant rate of 1.1 m/s^2 for a time of 3 seconds. What is the velocity at the end of this time?
5.3 m/s V= (2 m/s) + (1.1 m/s^2)*3
It is estimated that 5 large pizzas are about right to serve a physics club meeting of 30 students. How many pizzas would be required if the group grew to 48 students?
8 pizzas (30 students/ 5 pizzas) * (48 students/ x pizzas)
A crate has a mass of 9.4 kg. What is the mass in grams? In milligrams?
9.4 kg *(1000 grams/ 1 kg)= 9400 grams 9.4 kg *(1000 grams/ 1 kg) *(1000 mg/ 1 gram)= 94 X 10^6 mg
electricity and magnetism
the subfield of electric and magnetic forces and electric current
Mechanics
the subfield of forces and motion
optics
the subfield of light
particle physics
the subfield of subatomic particles
Thermodynamics
the subfield of temperature, heat, and energy
nuclear physics
the subfield of the nucleus of the atom
condensed-matter physics
the subfield of the properties of matter in the solid and liquid states
atomic physics
the subfield of the structure and behavior of atoms
A ball attached to a string is whirled in a horizontal circle such that it moves with constant speed. Does the velocity of the ball change in this process?
yes, because the direction is changing as the ball spins
A runner traveling with an initial velocity of 2 m/s accelerates at a constant rate of 1.1 m/s^2 for a time of 3 seconds. What distance does the runner cover during this process?
10.95 m d= v0t + 1/2at^2 = 3*(2 m/s) + 1/2*(1.1 m/s^2)*(9 s^2)
Suppose that a pancake recipe designed to feed three people calls for 600 mL of flour. How many millimeters of flour would you use if you wanted to extend the recipe to feed five people?
1000 mL (3 people/ 600 mL) * (5 people/ x mL)
what are the advantages and disadvantages of using a man's hand for a common unit?
advantage: also readily available disadvantage: the width of a man's hand is inconstant amongst multiple people
Starting from rest, a car accelerates at a constant rate of 3 m/s^2 for a time of 5 seconds. Compute the distance traveled by the car for these same times (1- 5 sec) and plot the distance against time.
d= 0 + 1/2(3 m/s^2)(x sec)^2= 1 sec= 1.5 meters 2 sec= 6 meters 3 sec= 13.5 meters 4 sec= 24 meters 5 sec= 37.5 meters *graph is exponential upwards with d (meters) vs. time (sec)
Does the speedometer on a car measure average speed or instantaneous speed? Explain.
instantaneous speed because it shows the speed that your car is going at that instant of time
which subfield is involved in describing how an acorn falls?
mechanics (force and motion of acorn)
which subfield is involved in the explanation of rainbows?
optics (produced by reflection of light off water droplets)
