Fisica Experimento 5

Introduction

The work W done by constant force acting on an object is equal to the product of the magnitudes of the component of the force F and the magnitude of the displacement x, both in the same direction, through which the force acts by the cosine of the angle ϴ between the force and displacement.

Objective:

To calculate experimentally work done by a constant force in magnitude, direction, and sense.

Theoretical analysis:

If the value of a force is known, can be calculated the work done, multiply the value of force by displacement f the object which the force is acting on it. Force produced by motion is constant, displacement in straight line and along on frictionless surface.

The situation to be analyzed is a glider of mass m1, sliding along rail, which is attached to second body with mass m2 by a rope that wrapped around pulley’s wheel.

Experimental work (W1). It is denoted in this way because we will refer to work calculated by experimental data: Given: W1= Fx

Where F is the acting force on glider with mass m1 and x is the displacement, then:

W1 = m1 ax1 and a = 2x/t2 since starts from rest and yield:

W1 = 2m1 x2/t2 Experimental work

Theoretical work (W2) is the work theoretically calculated for ideal case, in which the friction force is neglected. As you will see, the force acting on the system composed by m1 and m2, is weight of mass m2, this is w2 = m2g and as w2 produces on system an acceleration a, then we have that w2 = (m1+ m2 ) a, according to Newton’s Second Law. Isolating acceleration:

a = w2/ m1 + m2 or a = m2g/ m1 +m2

If we consider work on mass m1, then:

w2 = fx and w2 = m1ax

Substituting acceleration, we have:

w2 = m1m2 / m1 + m2 gx Theoretical work

Procedure:

1. Set up the linear air track and verify the level.

2. Mount and the pulley is centered relative to the hole of equipment, attach mass with threat to the glider with timing flag.

3. Set up the photo gates over metallic ruler and connect them to the digital stopwatch, in a mannerntha photo gate closer to glider must be record initial time of motion and second photo gate must record the time interval (∆t) recorder by stopwatch.

4. Turn on the air pump and stopwatch, select appropriate time scale.

5. Place the glider with timing flag centered on photo gate and stopwatch is stopped.

6. Release the glider and starts stop watch when the timing flag glider passes in front of the first photo gate and stopwatch is stopped when passes in front of second photo gate.

7. Measure the glider mass, mass hunger and masses, distance between photo gates should be 80 cm. The experiment is repeated two or more times in order to obtain an average time.

Table

Test M1 (g) M2 (g) x (cm) X2(cm2) T(s) t2 (s2)

1 143.6 cm 10

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