Motion 1 Solutions.notebook

Transcription

1 Question 1 In a race, a runner traveled 12 meters in 4.0 seconds as she accelerated uniformly from rest. The magnitude of the acceleration of the runner was m/s m/s m/s m/s 2 1

2 Question 2 A car traveling west in a straight line on a highway decreases its speed from 30.0 meters per second to 23.0 meters per second in 2.00 seconds. The car s average acceleration during this time interval is m/s 2 east m/s 2 west m/s 2 east m/s 2 west Answer1 Acceleration is a vector quantity with both magnitude and direction. Since the car s velocity is decreasing, the final velocity is less than the initial velocity. The change in the magnitude of the car s velocity will result in a negative value. 2

3 3. Which term identifies a scalar quantity? 1. displacement = distance in a direction (vector) 2. momentum = mass * velocity (vector) 3. velocity = speed in a direction (vector) 4. time = only a scalar, no directional dependence A vector quantity has both magnitude and direction associated with it. A scalar quantity has magnitude only and no direction associated with it. Time is the only quantity listed here that does not have a specific direction. Displacement, momentum and velocity are vector quantities; each has a direction associated with its magnitude. 3

4 Question 4 Which quantity has both a magnitude and a direction? 1. energy 2. impulse = Force * time (vector) 3. power = Work energy / time 4. work = Force * distance Answer2 A scalar quantity only has magnitude. Impulse is the product of force acting over a period of time. This is a vector quantity. 4

5 Question 5 A child riding a bicycle at 15 meters per second accelerates at 3.0 meters per second 2 for 4.0 seconds. What is the child s speed at the end of this 4.0 second interval? m/s m/s m/s m/s Answer3 The final speed at the end of 4.0 seconds is related to the initial speed and the magnitude of the acceleration during those 4.0 seconds. The final speed at the end of 4.0 seconds depends on the initial speed, the time, and the magnitude of the acceleration. 5

6 Question 6 A car, initially traveling east with a speed of 5.0 meters per second, is accelerated uniformly at 2.0 meters per second 2 east for 10. seconds along a straight line. During this 10. second interval the car travels a total distance of m m m m = 150 m Answer4 The car is traveling at 5.0 m/s for the 10. seconds with an additional acceleration of 2.0 m/s 2 during that 10. seconds. The car is traveling at 5.0 m/s for the 10. seconds with an additional acceleration of 2.0 m/s 2 during that 10. seconds. 6

7 Question 7 The graph below shows the relationship between the speed and elapsed time for an object falling freely from rest near the surface of a planet. What is the total distance the object falls during the first 3.0 seconds? 12 m 24 m 44 m 72 m Answer1 The question does not say Earth is the planet, but you can solve this problem in two different ways by using the data from the graph. One way to solve this problem is to calculate the area under the curve, which will give you the total distance travelled in 3.0 seconds. 7

8 Question 8 An object accelerates uniformly from 3.0 meters per second east to 8.0 meters per second east in 2.0 seconds. What is the magnitude of the acceleration of the object? m/s m/s m/s m/s 2 Answer1 Uniform acceleration occurs when an object gains the same amount of velocity in the same amount of time. 8

9 Question 9 If a car accelerates uniformly from rest to 15 meters per second over a distance of 100. meters, the magnitude of the car s acceleration is m/s m/s m/s m/s 2 Answer2 Which equation relates the given variables of final velocity and distance? 9

10 Question 10 A car traveling on a straight road at 15.0 meters per second accelerates uniformly to a speed of 21.0 meters per second in 12.0 seconds. The total distance traveled by the car in this 12.0 second time interval is m m m m Answer3 What is the car s acceleration? 10

11 Question 11 A high speed train in Japan travels a distance of 300. kilometers in seconds. What is the average speed of this train? m/s m/s m/s m/s Answer4 We can apply the equation for average speed, but remember that the distance the train travels is given in kilometers. 11

12 Question 12 Which quantity is a vector? 1. impulse = Force * time = change in momentum 2. power = work / time 3. speed = distance / time 4. time Answer1 A vector quantity has both magnitude and direction. From the list of quantities in the question only impulse (force time) is a vector quantity with both magnitude and direction. Speed is a scalar quantity related to velocity, which is a vector quantity. 12

13 Question 13 On a highway, a car is driven 80. kilometers during the first 1.00 hour of travel, 50. kilometers during the next 0.50 hour, and 40. kilometers in the final 0.50 hour. What is the car s average speed for the entire trip? km/h km/h km/h km/h Answer3 13

14 Question 14 The graph below represents the displacement of an object moving in a straight line as a function of time. What was the total distance traveled by the object during the 10.0 second time interval? 0 m 8 m 16 m 24 m Answer4 This is a displacement vs. time graph, not a distance vs. time graph. The total distance traveled as indicated by this displacement vs. time graph is 24 meters. The object traveled 16 m forward and then back another 8 m for a total of 24 m. The displacement, the straight line 14

15 Question 15 The speedometer in a car does not measure the car s velocity because velocity is a 1. vector quantity and has a direction associated with it 2. vector quantity and does not have a direction associated with it 3. scalar quantity and has a direction associated with it 4. scalar quantity and does not have a direction associated with it Answer1 Force is a vector quantity. Vector quantities have both magnitude and direction, while scalar quantities only have magnitude. 15