The laboratory work N^o 4.

Study of a rotational motion.

Had done by the student gr: 220473я F.N.S. Pavlov F.E.

Checked by ______________________ date ____________

Purpose: to study the dependence of angular acceleration of the body rotating comparatively to the motionless axis, from the net moment of acting on him forces.

The order of performing a work:

1. Rotating a pendulum for spokes A, wind a thread on a pulley B and to lift a cargo C of weight m specified it, on greatest possible height h.

2. To measure a time of falling a cargo (5 times). Evaluate an average time <t> of falling a cargo. Evaluate a torque by formula and angular acceleration by formula . To measure by ruler h and r(the radius of pulley, on which winded a thread).

3. Most to do, adding for a cargo supplementary weights .

4. Write data of measurements and calculations in the table 1.

5. Construct a plot of dependence .

6. Define by the plot : a) a moment of inertia of the cross;

b) a moment of friction force , modulus of which is equal

regression intercept OD.

Theoretical description:

We got a formula

Where y-y₀=h, V_0y = 0, a_y = 0, because of this:

Further follows, a_r= r

Because of the second Newton's law we can write:

In the projection on axis y:

We have chosen. That a_y = a, g_y = y, F_y = -F, so

So,

And the result for M is:

N	m1, kg	t, s	<t>, s	, rad/s2	M, Nm
1	0.1461	8.95	8.884	0.6969	0.0292
		8.82
		8.65
		9.10
		8.90
2	0.1944	7.22	7.312	1.0287	0.0388
		7.64
		7.15
		7.35
		7.20
3	0.239	6.64	6.232	1.4161	0.0477
		6.02
		6.05
		6.45
		6.00

0

From the plot we can calculate the moment of inertia: J=M/, so J= 0.0286 kgm²/rad, and the moment of the force of friction: M_f =1.12 Нm

Conclusion: so we have learned the dependence of angular acceleration of the body rotating comparatively to the motionless axis, from the net moment of acting on him forces.