1.2 Problems
9
1.2.4 Force and Torque
1.39 Three vector forces F 1 , F 2 and F 3 act on a particle of mass m = 3.80 kg as
shown in Fig. 1.7:
(i) Calculate the magnitude and direction of the net force acting on the
particle.
(ii) Calculate the particle’s acceleration.
(iii) If an additional stabilizing force F 4 is applied to create an equilibrium
condition with a resultant net force of zero, what would be the magnitude
and direction of F 4 ?
Fig. 1.7
1.40 (a) A thin cylindrical wheel of radius r = 40 cm is allowed to spin on a
frictionless axle. The wheel, which is initially at rest, has a tangential
force applied at right angles to its radius of magnitude 50 N as shown in
Fig. 1.8a. The wheel has a moment of inertia equal to 20 kg m 2 .
Fig. 1.8a
Calculate
(i) The torque applied to the wheel
(ii) The angular acceleration of the wheel
(iii) The angular velocity of the wheel after 3 s
(iv) The total angle swept out in this time
(b) The same wheel now has the same force applied but inclined at an angle
of 20 ◦ to the tangent as shown in Fig. 1.8b. Calculate
(i) The torque applied to the wheel
(ii) The angular acceleration of the wheel
[University of Aberystwyth, Wales 2005]