Chap 1 – 3: College Physics Quizzes – Flashcards
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conversion of units
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changing a number from one unit to another
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dimension
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represents physical nature and type of unit used to specify a quantity
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dinensional analysis
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a method for checking mathematical relations for the consistency of their dimensions
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scalar quanity
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a quantity described completely by its magnitude
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vector quantity
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a quantity with both magnitude and direction
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Kinematics
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deals with the concepts that are needed to describe motion without any reference to forces
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Dynamics
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deals with the effect that forces have on motion
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Mechanics
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the branch of physics that combines kinematics and dynamics
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Displacement
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a vector that points from an object's initial position to its final position and has a magnitude that equals the shortest distance between the two positions
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Average speed
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distance divided by elapsed time
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Average velocity
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displacement divided by elapsed time
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Instantaneous velocity
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indicates the speed and direction of an object at a specific point in time
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Instantaneous speed
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the magnitude of instantaneous velocity
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Average acceleration
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change in velocity divided by change in time
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Instantaneous acceleration
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indicates the change in velocity at a specific point in time
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Free-fall
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the idealized motion in which air resistance is neglected and the acceleration is nearly constant
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Acceleration due to gravity
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the acceleration of a freely falling body; usually 9.80 m/s2
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Slope
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displacement divided by change in time
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This is the unusual path of a confused football player. After receiving a kickoff at his own goal, he runs downfield to within inches of a touchdown, then reverses direction and races back until he is tackled at the exact location where he first caught the ball. The length of the football field is 100 yard. During this run, which took 25 second, what is 1. the path length he travels 2. his displacement 3. his average velocity in the x-direction 4. What is his average speed?
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1. 100 yards x 2 = 200 yards 2. Delta X = Xf - Xi = 0 - 0 = 0 (or Delta V x Delta t = 0 x 25 = 0) 3. V = Vf - Vi = 0 - 0 = 0 (or Delta V = Displacement change/time change = 0/25(s) = 0 4. Average speed = total distance/time = 200 yards/25seconds = 8 yrd/s
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A car must always have an acceleration in the same direction as its velocity 1. True 2. False
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False - acceleration can be positive or negative. So can velocity; e.g. + v and + a: the object moves to the right and accelerate (go faster) + v and - a: the object moves to the right and slow down ect....
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It is possible for a slowing car to have a positive acceleration 1. True 2. False
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True - The car moves to the left (negative velocity), but accelerate to the right (positive acceleration), so the car moves to the left and slow down
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An object with constant nonzero acceleration can never stop and remain at rest 1. True 2. False
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True
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A tennis player on serve tosses a ball straight up. While the ball is in free fall, does its acceleration 1. Increase 2. Decrease 3. Increase and then decrease 4. Decrease and then increase 5. Remain constant
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Remain constant Explanation: A freely falling object is any object moving freely under the influence of gravity ALONE, regardless of its initial motion. Gravity is constant
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As the tennis ball travels through the air, does its speed 1. Increase 2. Decrease 3. Increase and then decrease 4. Decrease and then increase 5. Remain the same
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Decrease and then increase Explanation: The ball is moving from Vi > 0 to V(at the peak) = 0; and then when the ball falls, it is moving from V(at the peak) = 0 to Vf > 0
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A skydiver jumps out of a hovering helicopter. A few seconds later, another skydiver jumps out, so they both fall along the same vertical line relative to the helicopter. Both skydivers fall with the same acceleration. 1. Does the vertical distance between them A. Increase B. Decrease C. Stay the same 2. Does the difference in their velocities A. Increase B. Decrease C. Stay the same
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1. A - Increase 2. C - Stay the same Explanation: The only force acting on them(air resistance aside) will be gravity. G=9.8 m/s = 10 m/s Diver 1 will fall for 3 seconds(30m/s) as Diver 2 starts falling(0m/s). After 1 second D1 will have fallen for 4 seconds and D2 will have fallen for 1 second. D1=g4=10m/s(4s)= 40m/s D2=g1=10m/s(1s)=10m/s
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The magnitude of two vectors: vector A and vector B are 12 unites and 8 units, respectively. What are the largest and smallest possible values for the magnitude of the resultant vector R = vector A + vector B 1. 14.4 and 4 2. 12 and 8 3. 20 and 4 4. none of these
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20 and 4 Possible largest = 12 + 8 = 20 Possible smallest = 12 - 8 = 4
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Vector A in quadrant II, vector B in quadrant IV. Determine the signs of the x- and y- components of 1. Vector A, vector B and 2. Vector A + Vector B
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1. Vector A: - Ax & +Ay. Vector B: +Ax and -Ay 2. -Ax and -Ay (the resultant vector is in quadrant IV)
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Which of the following objects can not be accelerating? 1. An object moving with a constant speed 2. An object moving with a constant velocity 3. An object moving along a curve
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An object moving with a constant velocity
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Consider the following controls in an automobile: gas, pedal, brake, steering wheel. The controls in this list that cause an acceleration of the car are 1. all three controls 2. the gas pedal and the brake 3. only the brake 4. only the gas pedal
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all three controls
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Suppose you are carrying a ball and running at constant speed, and wish to throw the ball and catch it as it comes back down. Should you 1. throw the ball at an angle of about 45 degree above the horizontal and maintain the same speed 2. throw the ball straight up in the air and slow down to catch it 3. throw the ball straight up in the air and maintain the same speed
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throw the ball straight up in the air and maintain the same speed
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As a projectile moves in its parabolic path, the velocity and acceleration vectors are perpendicular to each other 1. everywhere along the projectile's path 2. at the peak of its path 3.nowhere along its path 4. not enough information given
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at the peak of its path
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A child rides a pony on a circular track and completes one lap; i.e. returns to the starting point. For this trip, 1. the _____ is greatest when the child is at the half-way point 2. the _____ is greatest when the child is back at the starting point A. Distance travel and displacement B. Displacement and distance traveled
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Displacement and distance traveled
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A race car accelerates at a uniform (constant) rate, going from 0 to 120 mph and traveling a distance of 1.0 mile in 60 seconds. At the 30 second mark, the car's velocity is (1)_____ and it has traveled a distance (2)_______ A. Less than 60 mph, equal to 1/2 mile B. Equal to 60 mph, less than 1/2 mile C. greater than 60 mph, greater than 1/2 mile D. equal to 60 mph, equal to 1/2 mile E. equal to 60 mph, greater than 1/2 mile
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Equal to 60 mph, less than 1/2 mile
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Vector A has a magnitude of 100m and is directed along the positive x-direction. Vector B has a magnitude of 75 m and is directed along the negative y-direction. 1. The vector A + B lies in what quadrant 2. The vector B - A lies in what quadrant
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1. Fourth 2. Third
