Physics MCQ Key - Questions and Answers (Complete Solutions) A ball of mass 0.4 kg is initially at rest on the ground. It is kicked and leaves the kicker's foot with a speed of 5.0 m/s in a direction 60° above the hori
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Physics MCQ Key - Questions and Answers (Complete Solutions) A ball of mass 0.4 kg is initially at rest on the ground. It is kicked and leaves the kicker's foot with a speed of 5.0 m/s in a direction 60° above the horizontal. The magnitude of the impulse imparted by the ball to the foot is most nearly 2 N*s A force of constant magnitude F and fixed direction acts on an object of mass m that is initially at rest. If the force acts for a time interval Δt over a displacement Δx , what is the magnitude of the resultant change in the linear momentum of the object? FΔt A person applies an impulse of 5.0 kg∙m/s to a box in order to set it in motion. If the person is in contact with the box for 0.25 s, what is the average force exerted by the person on the box? 20.0N An object of known mass M with speed vo travels toward a wall. The object collides with it and bounces away from the wall in the opposite direction in which the object was initially traveling. The wall exerts an average force Fo on the object during the collision. A student must use the equation \Delta p=F\Delta tΔp=FΔt to determine the change in momentum of the object from immediately before the collision to immediately after the collision. Which side of the equation could the student use to determine the change of the object's momentum? Neither side of the equation may be used because there are too many unknown quantities before, during, and after the collision. In an experiment, an object is released from rest near and above Earth's surface. A student must determine the relationship between the direction of the gravitational force exerted on the object and the change in momentum caused by that force. What data could the student collect to determine the magnitude and direction of the gravitational force and the change in momentum of the object? Justify your choices. Select two answers. The mass of the object, because it is required to determine the force due to gravity exerted on the object, and the velocity of the object the instant before it reaches Earth's surface, because it is required to determine the change in velocity of the object. The mass of the object, because it is required to determine the force due to gravity exerted on the object, and the distance fallen by the object, because the force is exerted during the entire falling distance. A student conducts an experiment in which an object travels across a horizontal surface while for 2s a net force is applied to a 2 kg object that initially travels with a speed of 0.5 m/s. Data collected from the experiment are used to create the graph of the magnitude of the applied force exerted on the object as a function of time is shown. All frictional forces are considered to be negligible. Can the student use the graph and the known data to determine the momentum of the object after the force has been applied? No, because the student needs to know the direction that the force is applied to the object because the applied force will be in the same direction as the change in momentum of the object. Cart A with a mass of 2.0 kg travels at a constant speed of 3.0 m/s to the right on a horizontal surface, as shown in the figure. Cart A then collides with cart B with a mass of 1.5 kg that is initially at rest... Equation 1 and Equation 2 An object of mass 2 kg collides with an object of mass 1 kg that is at rest, as shown in the figure. A graph of the force as a function of time that the 1 kg object exerts on the 2 kg object is shown. (2 kg) (2m/s-v0)=1/2(8000 N)(0.00125 s) How does an air mattress protect a stunt person landing on the ground after a stunt? It lengthens the stopping time of the stunt person and reduces the force applied during the landing. Ball X of mass 1.0 kg and ball Y of mass .5 kg travel toward each other on a horizontal surface... ball Y will travel at a speed greater Assume that the collision in each scenario is elastic. A graph of the magnitude of the force exerted on Cart Y as a function of time for scenario 1 is shown. During which interval of time does the magnitude of the momentum of Cart Y change the most? .004s to .006s A student drops an object from rest above a force plate that records information about the force exerted on the object as a function of time during the time interval in which the object is in contact with the force plate. Which of the following measurements should the student take, in addition to the measurements from the force plate, to determine the change in momentum of the object from immediately before the collision to immediately after the collision? The student has enough information to make the determination. The student conducts a second experiment in which the magnitude of the force exerted on block X from block Y is measured over the time in which the collision takes place. A graph of the force as a function of time is shown. In a third experiment, the student creates a collision such that the force exerted on block X from block Y is constant for 0.020 s. Which of the following constant forces, if exerted on block X from block Y, would produce the same change in momentum as is shown by the graph? 200N A student must determine a nonzero change in momentum of an object for a specific interval of time. Which of the following experiments could the student conduct? Select two answers. drop a ball and give a block A student must conduct an experiment in which a block is pulled across a horizontal surface by a spring scale so that a nonzero change in momentum of the block can be determined for a specific time interval. The student also has access to measuring tools that are found in a typical physics laboratory. Which of the following experiments could the student conduct to determine the change in momentum of the cart? Select two answers. Attach the spring scale to the block, and pull the block so that its speed increases as it travels across the horizontal surface. Record the force that the spring scale exerts on the block. Use a stopwatch to determine the time that the block is in motion. Attach the spring scale to the block, and pull the block so that its speed increases as it travels across the horizontal surface. Use the motion detector to record the speed of the block at the beginning of the time interval and at the end of the time interval. Use a mass balance to measure the mass of the block. An object is used in three different experiments so that a student can analyze the motion of the object when a net force is exerted on it. The data obtained from the three experiments are shown in the table. How can the student use the data to determine the relationship between the object's change in momentum and the direction of the net force exerted on the object? The student can calculate the change in the velocity of the object for each experiment. If the object decreases its speed or changes direction, the net force changes the momentum in the opposite direction of motion. If the object increases its speed and travels in the same direction, the net force changes the momentum in the same direction of motion. An object of mass 5kg travels in the positive direction with a speed of 1m/s. The object collides with a second object that exerts an average net force over an interval of time such that the 5kg object comes to rest. Which of the following best predicts the change in momentum for the 5kg object? in the negative direction A student conducts three experiments in which a cart of mass M is pushed along a horizontal surface of negligible friction for 20s by an applied force. The graph shows the force as a function of time for each experiment. Which of the following correctly ranks the greatest change in the cart's momentum from 0s to 20s? Experiment 3 =experiment 2= experiment 1 A ball is released from rest above a horizontal surface. The ball falls downward and collides with the surface with a speed of 2.0m/s. The average force exerted during the
collision is 20N over a time interval of 0.1s. Which of the following best predicts what will happen to the ball immediately after the collision? The ball will come to rest on the surface Two model cars, A and B, have the same mass but different bumpers. The acceleration of each car during its collision with a wall is measured, and the data are shown in the graphs above. Which of the following statements about the collisions are correct? Select two answers. The cars, the change A student obtains data on the magnitude of force applied to an object as a function of time and displays the data on the graph above. Answer the following question for the information and diagram above. The increase in the momentum of the object between t = 0 s and t = 4 s is most nearly 60 N*s A spacecraft of mass 4000 kg is traveling in a straight line in the positive direction. Engines can be fired so that the force exerted on the spacecraft is in the positive or negative direction. The graph above shows data for the force during one interval. Which of the following is the best estimate of the net change in the speed of the spacecraft from time t = 0 to time t = 4 s? +.1m/s A cart of known mass moves with known speed along a level, frictionless track, as shown in the figure above. The cart hits a force sensor and rebounds. The force sensor measures the force exerted on the cart as a function of time and as a function of the position of the cart. The results will be graphed on the axes shown. Which of the two graphs can be used to determine the cart's speed after it rebounds? Either Which of the following is a true statement about the conservation of linear momentum? It is conserved only when no net external force acts on the system under consideration. A ball is dropped and bounces off the floor. Its speed is the same immediately before and immediately after the collision. The ball's momentum changes direction but not magnitude A 12 kg box sliding on a horizontal floor has an initial speed of 4.0 m/s. The coefficient of friction between the box and the floor is 0.20. The box moves a distance of 4.0 m in 2.0 s. The magnitude of the change in momentum of the box during this time is most nearly 48 A kitten sits in a lightweight basket near the edge of a table. A person accidentally knocks the basket off the table. As the kitten and basket fall, the kitten rolls, turns, kicks, and catches the basket in its claws. The basket lands on the floor with the kitten safely inside. If air resistance is negligible, what is the acceleration of the kitten-basket system while the kitten and basket are in midair? The acceleration is directed downward with magnitude equal to g because the system is a projectile. A cart of mass 1kg travels along a horizontal, frictionless surface. A net force is applied to the cart. A graph of the net force applied to the cart as a function of time is shown. The initial and final direction of the cart and the direction of the net force exerted on the cart are unknown. The distance of one grid unit represents a change in velocity of 1 m/s. Which of the following diagrams could represent the direction and relative magnitude of the velocity of the cart before the force is applied and after the force is applied? Select two answers. AD A student performs an experiment in which two blocks, block X of mass 2kg and block Y of mass 3kg, are tied together by a rope. The system containing Block X and Block Y is dropped above Earth's surface in the orientation shown in Figure 1. A motion detector below each block collected data that were graphed to show the velocity as a function of time for Blocks X and Y as they fell toward the ground. The graphs are shown in Figure 2 and Figure 3, respectively. The positive direction is considered to be down. The change in momentum for the system containing block X and block Y is most nearly 250 A 2kg object travels in the positive direction across a horizontal surface with a constant speed of 10 m/s. A force is exerted on the object for 4s, and the force increases linearly with respect to time. The table shows data about the magnitude of the applied force exerted on the object at different times. The force is exerted on the object in the opposite direction of the object's displacement. What is the change in momentum of the object? 8 negative A dart of mass md is launched straight upward toward a block of mass mb that hangs at rest from a string, as shown in Figure 1. Immediately before the dart collides with the block, the dart has a speed v0. The dart then collides with and sticks to the block, and the dart-block system travels upward to a height H before the system comes to rest, as shown in Figure 2. What is the change in momentum of the dart-block system immediately before the collision to the instant when the system comes to rest? -mdvo Two identical spaceships are traveling in deep space, far from any planets or stars. The ships travel in the same direction, with the slower one directly behind the faster one. The ships are connected by a cable attached to a spool, so that the part of the cable outside the ships can be made longer or shorter as needed. The cable is used to bring
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