Physics Chapter 11  Motion  Quiz Questions (#1 #6)

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A11: Define DISPLACEMENT. 
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A11: The change in position of an object. 
Q12: Define SPEED. 
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A12: The distance traveled divided by the time interval during which the motion occurred. 
Q13: Define VELOCITY 
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A13: The speed of an object in a particular direction. 
Q14: Which should you use in calculating how many gallons of gas you will need to make a road trip – distance or displacement? Give your answer and explain. 
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A14: Distance. Speed is the total distance covered, divided by the time it took to cover that distance. 
Q15: Explain the concept of “frame of reference.” 
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A15: A system for specifying the precise location of objects in space and time. 
Q16: You are on a boat going down a river at 5 km/hr. The river is flowing in the same direction at 2 km/hr. What is the combined speed of the boat? What would the speed of the boat be if you reversed your direction of travel and went upstream? 
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A16: 5 km/hr + 2 km/hr = 7 km/hr If the river current and the boat are going in the same direction, you ADD the speeds together. If you reversed direction, you subtract. 5km/hr  2km/hr = 3 km/hr. 
Q17: What is the formula for determining average speed? 
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A17: V = D T Velocity = Distance Time 
Q18: What is meant by the term “instantaneous speed?” 
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A18: Speed measured in a very small time interval (as with a car's speedometer). 
Q19: What does the term “average speed” mean? 
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A19: Average speed is the distance traveled divided by the total time taken. Some parts of the trip could be slow, others fast. For instance, if you traveled home from school your car might at times be traveling fast, other times slow, and still others not moving at all for a stop light. 
Q110: You are in a car traveling forward at 35 miles/hr. It is raining. There is no wind. Why does the rain appear to be coming straight towards the windshield? 
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A110: This is a frame of reference problem. Drops of rain appear to be coming straight at the windshield because you are driving into them. It is really just an optical illusion. In reality, the rain drops continue to fall straight down. 
Q111: List 3 units of measurement for … a) distance, b) time, c) speed, d) velocity 
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A111: a) m. , km. , cm. 
Q112: Speed is dependent upon what two factors? 
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A112: Distance and time 
Q113: What is the difference between SPEED and VELOCITY? 
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A113: Velocity is speed in a particular direction. With speed, no direction is given. 
Q114: CAR #1 is going 25 km/hr on the highway. CAR #2, going 50 km/hr just passedCar #1. a) If your frame of reference is car #1, what is the speed of car #2? b) If your frame of reference is car #2, what is the speed of car #1? 
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A114: a) Car #2 is going 25km/hr forwards b) Car #1 is going 25 km/hr backwards 
Q115: A skateboard is heading towards a tree at 3 km/hr. Describe what you see from these frames of reference: a) the skateboarderlooking at feet, b) bystanderon the sidewalk , c) skateboarderlooking at the tree. 
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A115: a) Skateboard is not moving = 0 km/hr 
Q21: What is an INDEPENDENT VARIABLE? 
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A21: Think of "independent" as not controllable. Time is a good example of an independent variable. 
Q22: What is a DEPENDENT VARIABLE? 
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A22: A dependent variable is one that you can change in an experiment. The dependent variable "depends on" the independent variable. For a distancetime graph, the dependent variable is distance. 
Q23: On a distance – time graph what is the “independent variable?” 
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A23: Time 
Q24: For line graphs which axis do you use for distance, which axis for time? 
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A24: distance > yaxis (the axis that goes UP) time > xaxis (the axis that goes across) 
Q25: If you have a distance – time graph of the speed of an automobile and it is NOT a straight line, what does that mean? 
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A25: That the car did not have a constant speed. It slowed down, sped up, or stopped for a period of time. 
Q26: On a distance – time graph for a vehicle moving at a constant speed, describe the slope of the line if the car is moving …. a) very fast, b) parked and not moving, c) moving slowly 
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A26: a) steep; b) horizontal; c) gradual slope 
Q27: Imagine that you could ride a baseball that is hit hard enough for a home run. Using the concept of frame of reference, describe what is happening from these perspectives: a) batter, b) you sitting on top of the baseball, c) outfielder trying to catch the hit. 
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A27: a) Ball speeds away from you; b) You are motionless, but the ground is moving past you quickly; c) The ball is approaching swiftly. 
Q28: Look at the three distance (vs) time graphs on page 371. What is the average speed of each car: a) Fastmoving car, b) Slowmoving car, c) Car with changing speed? 
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A28: a) 30 m/s b) 10 m/s c) 12 m/s 
Q29: Look at the Distance Vs. Time graph on the bottom lefthand corner of page 370. Visually compare the red line with the blue line and green line. Calculate the slope of the red line. 
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A29: 16m/4s = 4m/s 
Q210: Using the Distance Vs. Time graph on the bottom lefthand corner of page 370, list the relative speeds (fast, medium, slow) of the colored lines: a) Red line, b) Green line, c) Blue line. 
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A210: a) fast 
Q31: Define ACCELERATION. 
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A31: The rate at which velocity changes over time; an object accelerates if its speed, direction, or both change. 
Q32: Acceleration can be a change in what two things? 
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A32: speed or direction 
Q33: Is it possible to constantly accelerate when never speeding up or slowing down? Why or why not? 
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A33: YES! If you are changing directions, as in going in a circle, then you are constantly accelerating, but you are not actually speeding up or slowing down. 
Q34: What is CENTRIPETAL ACCELERATION? 
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A34: The acceleration that occurs in circular motion. 
Q35: What is the formula for acceleration? 
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A35: A = FV  OV 
Q36: If an objects starts at rest, what is its initial velocity? 
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A36: zero (0) 
Q37: How would the answer to an acceleration problem be shown if an object is slowing down? 
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A37: With a minus sign, as in 
Q38: List three examples of positive acceleration. 
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A38: car speeding up, plane taking off, you on your bicycle starting from a stand still. 
Q39: List three examples of negative acceleration. 
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A39: car slowing down, plane landing, you on your bicycle coming to a stop 
Q310: List three examples of acceleration due to a change in direction. 
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A310: a car turning a corner, you on a ferris wheel, an ice skater spinning in a circle 
Q311: Word Problem: Natalie begins from a stop and then accelerates her skateboard to 4 m/s in 2.5s. What is her acceleration? 
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A311: A = ? FV=4m/s OV=0m/s T=2.5s 
Q312: Word Problem: A turtle is swimming towards shore at 0.5 m/s. After 4s, its speed has increased to 0.8 m/s. What is the turtle’s acceleration? 
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A312: A=? FV=.8m/s OV=.5m/s T=4s 
Q41: Define the word FORCE. 
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A41: An action exerted on a body in order to change the body's state of rest or motion; force has magnitude and direction. 
Q42: What are the four FUNDAMENTAL FORCES? 
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A42: a) weak force (radioactive decay); b) strong force (binds protons & neutrons together); c) electromagnetic force; d) gravitational force 
Q43: Give two examples of FIELD FORCES. 
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A43: Electronagnetic & gravitational forces. 
Q44: What are BALANCED FORCES? 
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A44: Forces that are equal and opposite in direction. They cancel out. 
Q45: What are UNBALANCED FORCES? 
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A45: Forces that are NOT equal or are NOT opposite in direction. Whenever there is a net force acting on an object, the object accelerates in the direction of the net force. 
Q46: Do balanced forces change motion? 
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A46: NO! If the forces are balanced, they cancel out so that no change in motion occurs. 
Q47: What is the NET FORCE acting on a piano if ….. a) two students are each putting a force of 100N on the piano from the same side, or b) if the students are pushing from opposite sides of the piano? 
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A47: a) 200 N (add them together) 
Q48: Using BALANCED or UNBALANCED to describe the forces you would prefer, consider these examples and state why you chose your answer: a) Building a house, b) Riding your bicycle, c) Sitting on top of a fence, d) Riding a roller coaster. 
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A48: a) balanced  so it doesn't fall down; b) unbalanced  so that the bike will move forward; c) balanced  so that you don't fall off; d) unbalanced  so the roller coaster will move. 
Q49: When an object is at rest, are any forces acting upon it? Explain. 
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A49: YES! Gravity is acting upon it and static friction is acting upon it. 
Q51: Define FRICTION. 
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A51: A force that opposes motion between two surfaces that are in contact. 
Q52: Define STATIC FRICTION. 
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A52: The force that resists the initiation of sliding motion between two surfaces thar are in contact and at rest. 
Q53: Define KINETIC FRICTION. 
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A53: The force that opposes the movement of two surfaces that are in contact and are sliding over each other. 
Q54: Explain what is happening with STATIC FRICTION when you push on an object but do not move it. 
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A54: The static friction is greater than the force you have used to push it. 
Q55: Why is static friction usually greater than kinetic friction? 
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A55: The forces between molecules on the two surfaces is usually greater than the force necessary to keep the object moving. 
Q56: List the three types of KINETIC FRICTION and provide an example of each. 
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A56: a)slidingsliding a box across a table; b) rollingbicycle moving down a sidewalk; c) fluidboat moving through water, or car moving through air 
Q57: How can you reduce friction for each of the three types of kinetic friction? 
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A57: a) slidingsmooth the surface, use a lubricant, add wheels; b) rollingmake tires thinner, smooth the surface, lubricate wheel hubs or axles; c)fluidsmooth the surface, have less surface in contact with the water or air, more aerodynamic shape. 
Q58: How can you INCREASE static friction? 
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A58: increase the weight of the object, make the surface rougher, increase the surface area 
A59: Describe three ways to reduce the force of friction between a heavy block and a table top. 
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A59: a) smoother surface, b) add wheels, c) reduce surface area 
Q510: What is the amount of static friction acting on a truck if the truck does not move and the force pulling the truck downhill is 2000N? (Note: answer must include number + direction of force). 
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A510: 2000N downhill 
Q511: How are balanced and unbalanced forces related to static and kinetic friction? 
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A511: As long as the object does not move, you have balanced forces. Once the object begins to move, you have unbalanced forces that have overcome static friction and now kinetic friction is present. 
Q512: What happens when a net force acts upon an object? 
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A512: The object moves in the direction of the net force. 
Q61: Define MOTION. 
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A61: When an object continuously changes position in comparison to a reference point. 
Q62: Define SPEED. 
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A62: How fast an object moves. Distance covered divided by total time. 
Q63: What is the formula for SPEED? 
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A63: V = D 
Q64: What kind of line is produced by using a distance – time graph to illustrate constant speed? 
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A64: a straight line 
Q65: What is ACCELERATION? 
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A65: A change in an object's velocity  speeding up, slowing down, or changing direction. 
Q66: What are the three things that acceleration can mean? 
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A66: speeding up, slowing down, or changing direction 
Q67: What is the formula for ACCELERATION? 
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A67: A = FV  OV 
Q68: What are the four fundamental forces in nature? 
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A68: Weak nuclear force, strong nuclear force, electromagnetic force, gravitational force 
Q69: Explain BALANCED and UNBALANCED forces. 
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A69: Balanced forces are equal and opposite in direction. Unbalanced forces are not equal or not opposite in direction. Unbalanced forces yield a NET FORCE. 
Q610: Define the word FRICTION. 
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A610: A force that opposes motion between two surfaces. 
Q611: List and explain the two types of friction. 
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A611: Static Friction  objects are at rest; Kinetic Friction  an object is in motion 