Mechanics Dynamics Free fall 1.3.07-01 What you can learn about … Linear motion due to constant acceleration Laws of falling bodies Gravitational acceleration Principle: A sphere falling freely covers certain distances. The falling time is measured and evaluated from diagrams. The acceleration due to gravity can be determined. Tasks: 1. To determine the functional relationship between height of fall and falling time (h = h(t)=1/2 gt2). 2. To determine the acceleration due to gravity. What you need: Falling sphere apparatus 02502.88 1 02502.00 1 consisting of: Release unit Impact switch 02503.00 1 Digital counter, 4 decades 13600.93 1 Support base -PASS- 02005.55 1 Right angle clamp -PASS- 02040.55 2 Plate holder 02062.00 1 Cursors, 1 pair 02201.00 1 Meter scale, demo, l = 1000 mm 03001.00 1 Support rod-PASS-, square, l = 1000 mm 02028.55 1 Connecting cord, l = 1000 mm, red 07363.01 2 Connecting cord, l = 1000 mm, blue 07363.04 2 Complete Equipment Set, Manual on CD-ROM included Free fall P2130701 Height of fall as a function of falling time. PHYWE Systeme GmbH & Co. KG · D - 37070 Göttingen Laboratory Experiments Physics 23 LEP 1.3.07 -01 Free fall Related topics Linear motion due to constant acceleration, laws of falling bodies, gravitational acceleration. Principle A sphere falling freely covers certain distances. The falling time is measured and evaluated from diagrams. The acceleration due to gravity can be determined. Equipment Falling sphere apparatus consisting of Release unit Impact switch Digital counter, 4 decades Support base -PASSRight angle clamp -PASSPlate holder Cursors, 1 pair Meter scale, demo, l = 1000 mm Support rod-PASS-, square, l = 1000 mm Fig.1: Experimental set-up for the free fall 02502.88 1 02502.00 02503.00 13600.93 02005.55 02040.55 02062.00 02201.00 03001.00 02028.55 1 1 1 1 2 1 1 1 1 Connecting cord, l = 1000 mm, red Connecting cord, l = 1000 mm, blue 07363.01 07363.04 2 2 Tasks 1. To determine the functional relationship between height of fall and falling time (h = h(t)=1/2 gt2). 2. To determine the acceleration due to gravity. Set-up and procedure The set up is shown in Fig. 1. An electrically conducting sphere is gripped in the release mechanism which closes the start circuit. The pan is adjusted, using the adjusting screw under the arrest switch, in such a way that a downward motion of a few tenths of a millimetre closes the stop circuit. The pan is raised by hand after each single measurement (initial position). For the effective determination of the height of fall using the marking on the release mechanism, the radius of the sphere must be taken into account (diameter 3/4 inch, approx. 19 mm). The aerodynamic drag of the sphere can be disregarded. Theory and evaluation If a body of mass m is accelerated from the state of rest in a S constant gravitational field (gravitational force m g , it performs a linear motion. By applying the coordinate system in a way that the x axis indicates the direction of motion and solving the corresponding one- dimensional equation of motion, we get: m d2h1t 2 dt2 m·g We obtain, for the initial conditions h (0) = 0 dh102 dt 0 the coordinate h as a function of time (see Fig.2): h1t2 1 2 gt 2 (1) The height is directly proportional to the square of time. This can be displayed by a representation of h(t2) as shown in Fig.3. From the regression line of the data, we can calculate the gravitational acceleration because the slopeis equal to 1/2 g according to equation (1). For this measurement, we receive: g = 9.77 m/s2. (Theoretical value: 9.81 m/s2) Fig.4 shows the values of the gravitational acceleration for different measurements (heights of fall). PHYWE series of publications • Laboratory Experiments • Physics • © PHYWE SYSTEME GMBH & Co. KG • D-37070 Göttingen 21307-01 1 LEP 1.3.07 -01 Free fall Fig.2: Height of fall as a function of falling time Fig.4: Measured values of the gravitational acceleration Fig.3: Height of fall as a function of the square of falling time 2 21307-01 PHYWE series of publications • Laboratory Experiments • Physics • © PHYWE SYSTEME GMBH & Co. KG • D-37070 Göttingen