What is a newton? A tennis player swings and hits the ball away. How does the force of the tennis racket affect the motion of the ball? Need serious help!! How can the momentum of a moving object be found? By multiplying its mass by its acceleration.
By dividing its change in distance trabeled by the time it travels. By dividing its velocity bu the. Newton's Third Law. Thus, it would require a greater amount of force or a longer amount of time or both to bring such an object to a halt. As the force acts upon the object for a given amount of time, the object's velocity is changed; and hence, the object's momentum is changed.
The concepts in the above paragraph should not seem like abstract information to you. You have observed this a number of times if you have watched the sport of football. In football, the defensive players apply a force for a given amount of time to stop the momentum of the offensive player who has the ball. You have also experienced this a multitude of times while driving. As you bring your car to a halt when approaching a stop sign or stoplight, the brakes serve to apply a force to the car for a given amount of time to change the car's momentum.
An object with momentum can be stopped if a force is applied against it for a given amount of time. A force acting for a given amount of time will change an object's momentum. Put another way, an unbalanced force always accelerates an object - either speeding it up or slowing it down. If the force acts opposite the object's motion, it slows the object down. If a force acts in the same direction as the object's motion, then the force speeds the object up. Either way, a force will change the velocity of an object.
And if the velocity of the object is changed, then the momentum of the object is changed. These concepts are merely an outgrowth of Newton's second law as discussed in an earlier unit.
This equation represents one of two primary principles to be used in the analysis of collisions during this unit. To truly understand the equation, it is important to understand its meaning in words.
In words, it could be said that the force times the time equals the mass times the change in velocity. The equation really says that the. In a collision, objects experience an impulse; the impulse causes and is equal to the change in momentum.
Consider a football halfback running down the football field and encountering a collision with a defensive back. The collision would change the halfback's speed and thus his momentum. If the motion was represented by a ticker tape diagram , it might appear as follows:. At approximately the tenth dot on the diagram, the collision occurs and lasts for a certain amount of time; in terms of dots, the collision lasts for a time equivalent to approximately nine dots.
In the halfback-defensive back collision, the halfback experiences a force that lasts for a certain amount of time to change his momentum. Since the collision causes the rightward-moving halfback to slow down, the force on the halfback must have been directed leftward. If the halfback experienced a force of N for 0.
In a collision, the impulse experienced by an object is always equal to the momentum change. Now consider a collision of a tennis ball with a wall. Depending on the physical properties of the ball and wall, the speed at which the ball rebounds from the wall upon colliding with it will vary. The diagrams below depict the changes in velocity of the same ball. For each representation vector diagram, velocity-time graph, and ticker tape pattern , indicate which case A or B has the greatest change in velocity, greatest acceleration , greatest momentum change, and greatest impulse.
Support each answer. Click the button to check your answer. See Answer a. The velocity change is greatest in case B. The acceleration is greatest in case B. Acceleration depends on velocity change and the velocity change is greatest in case B as stated above.
The momentum change is greatest in case B. The impulse is given by the magnitude of the force times the time interval: We can see that the force F of the 4 skateboard is always the same 33 N , this means that the skateboard with greatest impulse is the one with the largest time interval, so skateboard C. Impulse has to do with time, it is the amount of force sustained for a period of time. You can increase the impulse by increasing the force applied or by increasing the period of time the force is applied.
Do you experience an impulse when you catch a ball of the same speed? Yes because when you catch the ball it exerts a force on you. This force has an impulse. Chapter 7 Review Answers: a Yes, when you throw a ball, you experience an impulse. Since this force pushes you, it exerts an impulse on you. Yes, to throw a ball, an impulse is exerted on it. An impulse is also exerted to catch it at the same speed.
The impulse exerted is twice the impulse exerted in either of the two cases above if the ball is caught and thrown back again with the same speed. Begin typing your search term above and press enter to search. Press ESC to cancel. Cannon Cannonball Both the same velocity change? Cannon Cannonball Both the same acceleration a? My Resources. Classroom News. My Homework. My Calendar. Kinematic Equations. Newtons 3rd Law. Notes on Acceleration Graphs. Notes on Forces.
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