Honors Physics Review

Transcription

1 Honors Physics Review Work, Power, & Energy (Chapter 5) o Free Body [Force] Diagrams Energy Work Kinetic energy Gravitational Potential Energy (using g = 9.81 m/s 2 ) Elastic Potential Energy Hooke s Law Thermal Energy (a.k.a., Heat) Power Mechanical Advantage Ideal Machines Ideal Mechanical Advantage o Work-Energy Theorem o Conservation of Energy o Simple Machines Impulse & Momentum (Chapter 6) o Impulse Graphs (Force vs. Time) o Newton s 3 rd Law o Vector Analysis/ Applying a Frame of Reference Impulse Momentum Change in Momentum Internal Forces (Action/ Reaction Pairs) o Conservation of Momentum o Collisions (4 types) Elastic Inelastic Perfectly Inelastic Explosion o Change in Kinetic Energy in Collisions (Heat Produced) Angular Kinematics (Part of Chapter 7) o Angular Motion Graphs Angular Displacement vs. Time Angular Velocity vs. Time Angular Acceleration vs. Time o Vector Analysis/ Applying a Frame of Reference o Applying Angular Kinematics Equations Centripetal Motion (Other Part of Chapter 7) Centripetal Acceleration Centripetal Forces o Free Body [Force] Diagrams o Applying Newton s Laws Horizontal Circles Vertical Circles Problems w/ Trig. Astronomy o Universal Gravitation (in Chapter 7) o g as a Function of r o Gravitational Potential Energy (using g = Gm/r 2 (downward) o Kinetic Energy o Kepler s Laws o Mr. Taylor s Power Point o Various Astronomers Other Stuff That You Should Already Know o Vectors vs. Scalars o Sin, Cos, Tan, & Pythagorean Thm. o Significant Figures o Labels o Newton s Laws of Motion

2 Practice Problems 1. Work, Power & Energy: A worker pulls an 18 kg box across a horizontal factory floor at a constant velocity of 2.4 m/s with an applied force of 43 N. The applied force is directed at a 37º angle above the floor, and the box moves 8.0 m. a) What are the mass of the box and the weight of the box. What s the difference between mass & weight? b) Draw a force diagram and define a frame of reference. c) How much work is done by the applied force? d) How much work is done by the normal force? e) How much work is done by the force of weight? f) What is the box s initial kinetic energy? g) What is the box s final kinetic energy? h) What is the box s change in kinetic energy? i) How much is the total work on the box? j) How is your answer from h) related to your answer for i)? k) How much work is done by the force of friction? l) What is another name for the work done by friction? m) What is the force of friction between the box and the floor? Is it static or kinetic? Why? n) What is the normal force on the box? o) What is the coefficient of friction between the box and the floor? p) How much heat is generated? [see parts k) and l)] q) What is the amount of power generated by the worker? 2. Work, Power & Energy: A worker pushes a 18 kg box up a 20º incline that is frictionless with an applied force of 73 N. The applied force is directed along the incline; the box starts from rest and moves 8.0 m up the incline. Find the following: a) The mass of the box and the weight of the box. What s the difference between mass & weight? b) Draw a force diagram and define a frame of reference. c) How much work is done by the applied force? d) How much work is done by the normal force? e) How much work is done by the force of weight? f) What is the box s change in gravitational potential energy? g) How is your answer from e) related to your answer for f)? h) How much is the total work on the box? i) What is the box s initial kinetic energy? j) What is the box s change in kinetic energy? k) How is your answer from h) related to your answer for j)? l) What is the box s final kinetic energy? m) What is the box s final speed? n) What was the box s acceleration? o) How much time did it take to move the box up the incline? p) What is the amount of power generated by the worker? q) What is the work input for the inclined plane? r) What is the work output for the inclined plane? s) What is the efficiency of the inclined plane? t) Why isn t there any heat generated in #2, but there was in #1? u) What would happen to your answer to part s) if the incline did have friction? v) What would be the work output if the incline generated as much heat as in #1 part p)? w) What would be the efficiency of the incline if it generated as much heat as in #1 part p)?

3 3. Energy Springs: A 12 g marble is accelerated from rest along a horizontal track by a compressed spring. It takes 28 N to compress the spring 6.0 cm. a) What is the spring constant (a.k.a., constant of elasticity) of the spring? b) How much energy is stored in the spring? c) How much kinetic energy does the marble have once it is released onto the track? d) How fast is the marble going once it is released onto the track? The track then goes into a loop-to-loop with a 1.0 m radius. e) What is the gravitational potential energy at the top of the loop? f) What is the kinetic energy at the top of the loop? g) What is the speed at the top of the loop? 4. Simple Machines: A force of 32 N is applied to a screwdriver handle to pry open the lid of a paint can. The handle is 12 cm from the lip of the can (a.k.a., the fulcrum). The flathead of the screwdriver then applies a force of 250 N to the lid which is 1.4 cm from the lip of the can. a) What type of lever is this? b) What is the work put into the lever by the person? c) What is the work that output from the lever? d) What is the efficiency of the lever? e) What is the mechanical advantage of the lever? f) What is the ideal mechanical advantage of the lever? g) Explain what the difference is between your answers for parts e) & f). 5. Impulse & Momentum: In a one-dimensional collision, a 4.0 kg bowling ball with a velocity of 4.5 m/s forward collides inelastically with a 1.0 kg bowling pin initially at rest. The pin has a velocity of 6.0 m/s forward after the collision. The collision takes place in a duration of s. Let forward be the + direction. a) What is the pin s initial momentum? b) What is the ball s initial momentum? c) What is the pin s final momentum? d) What is the ball s final momentum? e) What is the ball s final velocity? f) What is the pin s change in momentum? g) What is the ball s change in momentum? h) How is your answer from part f) related to your answer for part g)? i) What is the impulse on the pin? j) How is your answer from part f) related to your answer for part i)? k) What is the impulse on the ball? l) How is your answer from part g) related to your answer for part k)? m) What is the force from the ball onto the pin? n) How much is the force of the pin on the ball? o) Which law verifies your answers for parts m) & n)? p) For the pin, sketch a graph of force versus time for the uniform collision between the ball and the pin? q) For the ball, sketch a graph of force versus time for the uniform collision between the ball and the pin? r) What is the pin s initial kinetic energy? s) What is the ball s initial kinetic energy? t) What is the total initial kinetic energy? u) What is the pin s final kinetic energy? v) What is the ball s final kinetic energy? w) What is the total final kinetic energy? x) What is the total change in kinetic energy? How does this differ from the total heat produced? y) In what type of collision would your answers to parts t) & w) be the same? z) In what type of collision would your answer to part w) be greater than your answer to part t)? aa) In what type of collision would your answer to part x) be a maximum value?

4 6. Angular Kinematics: A bike wheel has a radius of 38 cm and starts from rest. A torque is applied such that it accelerates at a rate of 0.60 rad/s 2 in the clockwise direction. It continues to angularly accelerate for 4.0 s. After 4.0 s, the wheel continues at constant angular velocity for a 3.0 s interval. It then slows uniformly for a 2.0 s interval at which time the wheel comes to rest. Let clockwise be the + direction. a) What is the angular velocity at 4.0 s? b) What is the angular displacement at 4.0 s? Suppose a piece of tape marks a point on the wheel s rim. c) What is the distance traveled (arc length) by the piece of tape at 4.0 s? d) What is the tangential speed of the piece of tape at 4.0 s? at 6.0 s? e) What is the centripetal acceleration of the tape? f) What is the angular acceleration of the wheel from 7.0 s to 9.0 s? g) What is the angular displacement of the wheel from 7.0 s to 9.0 s? h) Sketch a graph of angular displacement vs. time for the wheel s 9.0 s of motion. i) What is the shape of the graph (be specific) from 0 s to 4.0 s? from 4.0 s to 7.0 s? from 7.0 s to 9.0 s? a. If any part of your graph was a straight line, what physical quantity does its slope b. If any part of your graph was a parabola, what physical quantity does a line tangent to the curve j) Sketch a graph of angular velocity versus vs. time for the wheel s 9.0 s of motion. k) What is the shape of the graph (be specific) from 0 s to 4.0 s? from 4.0 s to 7.0 s? from 7.0 s to 9.0 s? a. What physical quantity does the slope of each time interval b. What physical quantity does the area between the graph and the time axis of each time interval l) Sketch a graph of angular acceleration versus vs. time for the wheel s 9.0 s of motion. m) What is the shape of the graph (be specific) from 0 s to 4.0 s? from 4.0 s to 7.0 s? from 7.0 s to 9.0 s? a. What physical quantity does the slope of each time interval b. What physical quantity does the area between the graph and the time axis of each time interval 7. Centripetal Motion Horizontal Circles: A 52 kg boy is standing on a merry-go-round at a distance of 1.5 m from the center (a.k.a., the radius). He spins at a constant rate and makes one revolution every 2.8 s. a) What are the boy s mass and weight? b) What are the period and frequency of the boy s motion? c) What is the boy s tangential speed? d) What is the boy s angular speed? e) What is the boy s centripetal acceleration? f) What is the boy s tangential acceleration? g) What is the boy s angular acceleration? h) Draw a free body (force) diagram & define a frame of reference. i) What is the normal force on the boy? j) What is the force of kinetic friction on the boy? k) What is the force of static friction on the boy? l) What is the coefficient of friction between the boy and the merry-go-round? Suppose the merry-go-round is replaced by a gravitron. The radius is increased to 4.0 m, and the boy is stuck to an outer wall instead of standing on the floor. He still spins at a constant rate of one revolution every 2.8 s. m) Repeat parts b) through k). If the result is the same as the merry-go-round, you may just write same. n) What is the coefficient of static friction between the boy and the wall?

5 8. Centripetal Motion Vertical Circles: An 820 N stunt pilot is flying his plane in circular loop-to-loops with a radius of 280 m. a) What are the pilot s mass and weight? b) Draw a free body (force) diagram for the pilot at the top of the loop if he is to experience weightlessness. c) At what speed will he feel weightless? Suppose the pilot s speed at the top of the loop is 40 m/s. d) Draw a free body (force) diagram for the pilot at the top of the loop. e) What will be the magnitude and direction of the force from the seat acting on the pilot? (normal force) f) Will the pilot feel upside down or right-side up? Will he feel heavier or lighter than normal? Suppose the pilot s speed at the top of the loop is 64 m/s. g) Draw a free body (force) diagram for the pilot at the top of the loop. h) What will be the magnitude and direction of the force from the seat acting on the pilot? (normal force) i) Will the pilot feel upside down or right-side up? Will he feel heavier or lighter than normal? Suppose the pilot s speed at the top of the loop is 78 m/s. j) Draw a free body (force) diagram for the pilot at the top of the loop. k) What will be the magnitude and direction of the force from the seat acting on the pilot? (normal force) l) Will the pilot feel upside down or right-side up? Will he feel heavier or lighter than normal? Suppose the pilot s speed at the bottom of the loop is 64 m/s. m) Draw a free body (force) diagram for the pilot at the bottom of the loop. n) What will be the magnitude and direction of the force from the seat acting on the pilot? (normal force) o) Will the pilot feel upside down or right-side up? Will he feel heavier or lighter than normal? 9. Centripetal Motion w/ Trig: A 350 g ball is on a string, and the ball is whirled around in a horizontal circle. The string has tension, F T, and makes angle, θ, with the vertical. The circle has a radius of 0.59 m, and the ball takes 0.55 s to complete one revolution. a) What is the mass of the ball? What is the weight of the ball? b) What is the angular speed of the ball? c) What is the tangential speed of the ball? d) What is the centripetal acceleration of the ball? e) Draw a free body (force) diagram for the ball. Include a frame of reference. f) What is the vertical component of F T? g) What is the centripetal force on the ball? h) What is the horizontal component of F T? i) What is the tension, F T? j) What is the angle, θ, between the string that the vertical reference line? **End of Review** This review did not include astronomy topics because those topics were recent! Astronomy will still be on the final exam.