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Unformatted text preview: / Physics 295 Introductory Laboratory I Partners Section Date LAB 4: COMBINING FORCES Nature and Nature's laws lay hid at night: God said, "Let Newton be!" and all was light. Alexander Pope OBJECTIVES To understand the relationship between the direction of the force applied to an object and the direction of the acceleration of the object. To understand how different forces can act together to make up a combinedforce. To establish a definition of combinedforce as that which changes the motion of an object in a consistent way. To understand the motion of an object with no force applied to it and how Newton's First Law describes this motion. Physics Material: Definition of force, Newton's Laws of Motion. OVERVIEW In previous labs you have examined the one-dimensional motions of an object caused by a single force applied to the object. You have seen that when friction is so small that it can be ignored, a single constant applied force will cause an object to have a constant acceleration. (The object will speed up at a steady rate.) Under these conditions, you have seen that the acceleration is proportional to the applied force, if the mass of the object is not changed. You saw that when a constant force is applied to a cart, the cart speeds up at a constant rate so that it has a constant acceleration. If the applied force is made larger, then the acceleration is proportionally larger. This allows you to define force more precisely not just in terms of the stretches of rubber bands and springs, but as the "thing" that causes acceleration. The major goal of this lab is to continue to develop the relationship between force and acceleration, an important part of the first two of Newton's famous laws of motion. @1993-94 P.Laws,D. Sokoloff,R. Thornton . Supported by National Science Foundation and the U.S.Dept. of Education (FIPSE) Note: These materials have been modified locally for use in the U of L laboratories. Page 4-1 Page 4-2 Real Time Physics: Active Learning Laboratory V1.40--8/94 In Investigation 1, you will explore motions in which the applied force (and hence the acceleration of the object) is in a different direction than the object's velocity. In this case the object is slowing down since its speed is decreasing. In Investigation 2, you will explore what happens when more than one force is applied to an object. INVESTIGATION 1: SPEEDING UP AND SLOWING DOWN In Lab 3 you have looked at cases where the velocity, force and acceleration all have the same sign (all positive). That is, the vectors representing each of these three vector quantities all point in the same direction. For example, if the cart is moving toward the right and a force is exerted toward the right, then the cart will speed up. Thus the acceleration is also toward the right. The three vectors can be represented as: Velocity Force Acceleration ~v ~F If the positive x direction is toward the right, then you could also say that the velocity, acceleration and force are all...
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