Chapter 11-12 Review
Frame of reference A vantage point by which motion is measured Solve: A car travels 30m/s relative to the ground. How fast is the passenger in back seat traveling: a. Relative to the car? b. Relative to the road?
Distance vs displacement Distance: total length traveled Displacement: total distance traveled from the starting point to the ending point that is a straight line Solve: You walk 2 km to school. During the day, you walk an additional 3 km between your classes and band practice. You then go to your friend’s house after school who lives 2 km from school and 1 km from your house. What total distance did you travel? What was your total displacement?
vectors A vector is a quantity that has both a magnitude (value) and direction. Examples: Force, velocity, acceleration, momentum, displacement, weight
Speed, velocity, and acceleration Speed = change in distance over time (S= 𝑑 𝑡 ) Velocity = change in distance over time with a direction (V= 𝑑 𝑡 ) Acceleration = change in speed or velocity over time (A= 𝑠 𝑡 )
Average speed The total distance covered by the total time it takes to cover that distance Solve: You take a trip to Miami (320 miles) and it takes you 5.5 hours to get there. What is your average speed for the trip?
Acceleration Solve: A car goes from a speed of 40 m/s to a speed of 30 m/s in 5 s. What is the car’s rate of acceleration?
Newton’s 1st law of motion An object will remain at rest or in motion unless acted upon by an unbalanced force. Also known as the law of inertia. Inertia: the tendency of an object to remain at constant velocity in a straight line forever
Newton’s 2nd law of motion Force = mass x acceleration Net force: the remaining force after a reaction has occurred Solve: A 6N force pushes on a 5 kg mass to the north. A 2N force pushes on the same mass with a force of 2N to the west. Find the resultant net force magnitude and direction acting on the 5 kg mass.
Newton’s 3rd law of motion Every action has an equal and opposite reaction
Momentum and collisions Momentum: the product of mass times velocity. Measured in kg m/s. P=mv Solve: What is the momentum of a 22 kg mass moving at a velocity of 3 m/s? In a collision, a 2 kg mass traveling at 3 m/s transfers all of its momentum to a stationary 2 kg mass. At what velocity does the stationary mass move off after the collision?
Friction The force that opposes motion Types of friction: sliding, rolling, static, and fluid Solve: Write down at least 2 examples of each type of friction on your paper.
Law of Universal gravitation All objects in the universe are attracted to one another. Gravity is dependent upon mass. Acceleration of gravity on the Earth is measured as 9.8 m/s2 Acceleration of gravity on the moon is 1.6 m/s2 Weight = mass x gravity Solve: On the surface of the Earth, Arnold weighs 400N. What does he weigh on the surface of the moon?
Fundamental Forces Gravitational: force of attraction between objects Electromagnetic: force of attraction or repulsion that is generated by electric current Strong Nuclear: force that keeps the protons and neutrons together in the nucleus of the atom Weak Nuclear: attractive force in nucleus that acts over short distance
Graphing overview For a distance vs time graph, the slope is equal to the speed For a displacement vs time graph, the slope is equal to the velocity For a speed vs time graph, the slope is equal to the acceleration A horizontal line on a distance vs time graph represents no motion A horizontal line on a speed vs time graph represents constant speed
Additional practice On the surface of the Earth, a box weighs 57N. What is its mass? A skydiver falls from a height of 10,000M for 5 seconds. What velocity is he traveling after the 5 seconds? A 25 kg cart sits on surface with 10N of friction. A 15N force is applied to it. What is the acceleration of the cart? On a table, a 20 kg mass is connected to a 10 kg mass that hang off the table. Both are connected by a pulley system. What is the acceleration of the 20 kg mass on the table as a result of this?