Physics assignment 1 (1)

41 Marks Total ASSIGNMENT 1 Part One: Momentum and Newton’s Second Law Part One of this assignment is worth 20 marks. Note: The answer areas will expand to fit the length of your response. All work must be shown for full marks to be awarded. 1. Identify and explain if one of the objects in each of these pairs has a greater value for the magnitude of its momentum than the other. (No calculations should be required.) (1) a 900.0-kg truck travelling at 60 km/h, or a 500.0-kg car travelling at 60 km/h Answer: Object 1 will have a greater momentum then object 2 because Object 1 has a greater mass resulting in a greater momentum then object 2 (1) a 15.0-kg object travelling to the right at 5.0 m/s, or a 15.0-kg object travelling to the left at 5.0 m/s Answer: Both of the objects have the same momentum although on is moving in the positive direction while one is moving in the negative direction (1) a 900-kg truck at rest, or a 500-kg car at rest Answer: Neither of the objects have momentum (1) a 900-kg truck at rest, or a mosquito flying at 2 m/s Answer: The mosquito has more momentum then the truck since it is at rest (3) 2. The momentum of a 75-g dart is 9.00 kg?m/s east. What is the velocity of the dart? As with all problems involving vectors, remember to include the direction in your answer. Answer: m=0.075kg p=9.00 kg?m/s{E} v=? v=p/m v=9.00 kg?m/s{E}/ 0.075kg v=120m/s{E} 3. A 425-g softball is travelling at 18.6 m/s [214o]. (2) What is the momentum of the softball? Answer: m=0.425kg v=18.6 m/s p=?p=mv p=0.425kg x 18.6 m/s p=7.91kgXm/s (1) Which of the four vectors below accurately shows the direction of the softball using the polar coordinates method as described on page 78 of the text? Answer: D (3) 4. What is the mass of a boat if it travels at a velocity of 57.0 km/h [E] and has a momentum of 2.15 x 106 kg?m/s [E]? Answer: v=15.83m/s [E] p=2.15 x 106 kg?m/s [E] m=? m=p/v m=2.15 x 106 kg?m/s [E]/ 15.83m/s [E] m=135818.067kg (2) 5. Use the concepts of momentum and Newton’s second law to explain why a motorcycle can accelerate at a greater rate than a large truck. To earn full marks for this question you should: Identify which vehicle has the larger momentum and use the equation for momentum to explain why this affects its ability to accelerate. Identify which vehicle can accelerate faster and use Newton’s second law to explain why. Answer: The large truck would have the larger momentum for it is heavier The motorcycle will accelerate faster because it has mass and will take less force too accelerate (5) 6. In video games, high-speed crashes are common. Consider a motorcycle and a scooter racing against each other down a mountain road. Neither driver will yield. Eventually each vehicle strikes a metal barrier. The concepts of momentum and net force can be used to make each simulated crash realistic. In a paragraph, explain how you would use the concept of momentum and net force to make each simulated crash realistic. In general, how could you use momentum and Newton's laws of motion to predict the amount that each section of the barrier changes shape? Would the stopping time for each vehicle be the same? Your answer should address the following questions: Compare the masses and speeds of each vehicle. (1 mark) Define momentum and compare the momentum values for each vehicle. (1 mark) Use the concept of impulse to explain the two variables that are required to change the momentum of each vehicle. (1 mark)  Describe how this is reflected in the change of shape of the barrier. (1 mark) Use the concept of Newton’s first law to explain what happens to each driver when they strike the barrier. (1 mark) Answer: The average mass and speed of a scooter is 115 kg and 26.8m/s. The average mass and speed of a motorcycle is 181kg and 44.7m/s. Momentum is a product of the mass and its velocity. It has both magnitude and direction. The momentum of the scooter is (3082kgm/s) The momentum of the motorcycle is (8090.7kgm/s). A larger net force acting over a smaller time interval, as well as a smaller net force active over a large time interval. Vehicles traveling at the same velocity come to a stop their impulse is the same regardless of how fast the stop or how much force they use to stop, their initial and final velocity are the same. Barriers are used halt the vehicle as it hits not too reduce the impact. An object in motion will stay in motion unless an acted on by an unbalanced force, meaning on a motorcycle or scooter hitting a barrier the motorcycle and scooter itself will come to rest but yourself is still in motion making you fly off the motorcycle or scooter until you hit the ground and come to rest. STOP! When you have completed all of the questions in Part One, save your work to your desktop. You will return to this assignment to complete Part Two after you have completed the remainder of the content in the changing momentum section. Part Two: Changing Momentum Part Two of this assignment is worth 21 marks. The value of each question is noted in the left margin in parenthesis. Note: The answer areas will expand to fit the length of your response. (3) 1. An arrow gains a momentum of 94.3 kg•m/s [W] in 0.400 s. Determine the magnitude and direction of the average unbalanced force that acted on the arrow. Answer: p=94.3 kg•m/s [W] t=0.400 s F=? Fxt=p F=p/t F=94.3 kg•m/s / 0.400 s F=236N{W} 2. An artillery shell is accelerated from rest and gains a momentum of 2.00 x 103 kg•m/s [E]. If the average net force acting on the shell was 8.50 x 103 N [E], calculate the time interval that this net force acted on the shell. Answer: p=2.00 x 103 kg•m/s [E]. F=8.50 x 103 N [E] t=? Ft=p t=p/F t=2.00 x 103 kg•m/s / 8.50 x 103 N t=0.24s 3. (3) A high school football player hits and pushes a tackling dummy during practice. The following graph shows the amount of force that acts on the player. What is the impulse that acts on the football player? Answer: ½(0.2s)(400N)=40NxS ½(1.0)(-800N)+-400NxS 40NxS+(-400NxS)= -360NxS (3) If the 60 kg player is running forward at 7.0 m/s when she makes contact with the dummy, what is the player’s velocity at the end of the 1.20 s impact? Answer: (60kg)(7.om/s)-(360N/s)=60N/s 60N/s / 60kg = 1m/s (1) From 0.0 s to 0.1 s, what is happening to the acceleration of the player? The player is accelerating at A. an increasing rate in the forward direction B. a decreasing rate in the forward direction C. a decreasing rate in the backward direction D. an increasing rate in the backward direction Answer: A (1) From 0.1 s to 0.2 s, what is happening to the acceleration of the player? The player is accelerating at A. an increasing rate in the forward direction B. a decreasing rate in the forward direction C. an increasing rate in the backward direction D. a decreasing rate in the backward direction Answer: B (1) During which time interval is the net force positive? Is the velocity increasing or decreasing when the force is positive? Answer: 0.0s-0.1s net force is positive. The velocity is increasing when it is positive (1) Identify and explain at which point in time the magnitude of the acceleration is the greatest. Answer: at 0.1s the magnitude is the greatest because of how much force was quickly used to get to that point (3) 4. The following illustration shows two ways of providing impulse to change the momentum of a vehicle. In the top illustration, the vehicle collides with a massive concrete barrier. In the bottom illustration, the vehicle collides with water-filled barrels. Explain which type of crash barrier would likely produce less damage to the vehicle and less injury to the occupants. Answer: The second car would have less damage to the car and less injury to the occupants because the concrete barrier is a fully stop meaning greater force and lower time to stop while the barrels will slowly halt the car to stop and has a greater time to make the car stop resulting in less damage and injury. (2) 5. On the basis of the contents of this lesson, explain the necessity of bicycle helmets to someone who does not believe they are necessary. Give two reasons. Answer: Without a helmet in the case of an accident you are more likely to injure your head if you hit a barrier you could fly off the bike and split your head open, and cause major brain issues if you aren’t wearing a helmet. Helmets reduce the force taken from impact and collision to the head. Helmets protect your face as well incase you of an accident you wont get as bad of road rash. When you have completed all of the questions in this assignment, submit your work to your teacher.