Question

(a) Why can’t you put your heels firmly against a wall and then bend over without falling? Explain. (b) Give an example in which the net force acting on an object is zero, yet the net torque is nonzero. (c) Give an example in which the net torque acting on an object is zero, yet the net force is nonzero.

Answer 1

a)

The cntre of gravity will balance the weight of the body.To remain in equilibrium, the center of gravity must always be over your point of support the feet. If heels are against the wall, the center of gravity cannot remain above feet . therefore, you will fall down when bent forward.

b)examples: are:

i) a rod rotate about an axis and two forces are acting perpendicular to the axis in opossite direction. in this case net force is zero but the torque is non-zero.

c) examples are:

i)If you have a wheel on a frictionless surface with a force pushing on the center this should move the wheel along rather then rotate it. in this casee net force non-zero but net torque is zero.

ii) consider a rod , when a force is pushing form the right in a direction that is parallel to the rod, the froce passes through the center of the rod in which there is no torque but the is net force.