Reading Quiz. 1. Viscous friction is ___ 1. larger than kinetic friction. ___ 2. equal to kinetic friction. ___ 3. smaller than kinetic friction. ___ 4. resistance to motion in fluids. 2. Torque is ___ 1. the way the British spell talk. ___ 2. related to ability to rotate a body.
1. Viscous friction is
___ 1. larger than kinetic friction.
___ 2. equal to kinetic friction.
___ 3. smaller than kinetic friction.
___ 4. resistance to motion in fluids.
___ 1. the way the British spell talk.
___ 2. related to ability to rotate a body.
___ 3. the product of force and distance.
___ 4. is a force.
___ 1. it is moving at constant speed.
___ 2. it cannot be rotating.
___ 3. there are no forces acting on it.
1) A 100 kg wooden crate is at rest on a level stone floor. Let .(a) What is the minimum horizontal force needed to start the crate moving? (b) What is the minimum horizontal force needed to keep the crate in motion at constant speed? (c) What will happen if a horizontal force of 500 N is applied to the crate? (d) What is the minimum non-horizontal force (directed at 30° from the horizontal, downwards) needed to start the crate moving?
1) The center of gravity of an object
____ a) is always at its geometrical center
____ b) is always in the interior of the object
____ c) may be outside the object
____ d) is sometimes arbitrary
____ e) is a real physical point
a) a uniform square
b) a uniform cube
c) a uniform equilateral triangle
d) a bowling ball
e) a uniform ring
f) a uniform boomerang
g) a tank half filled with water and half oil
h) a thermometer at very low temperature
1) A person exerts a force of 45 N on the end of a door 84 cm wide. What is the magnitude of the torque if the force is exerted (a) perpendicular to the door, and (b) at a 60 angle to the face of the door?
2) A couple consists of two forces of equal magnitude that act in opposite directions along parallel lines of action a distance d apart. If the magnitude of each force is F what is the torque exerted by a couple?
1) In an equilibrium problem the point about which torques are computed
____ a) must pass through one end of the object
____ b) must pass through the object’s center of gravity
____ c) must intersect the line of action of at least one force acting on the object
____ d) may be located anywhere
1) Three boys are trying to balance on a seesaw, which consists of a fulcrum rock, acting as a pivot at the center, and a very light board 3.6 m long. Two boys are already on either end. One has a mass of 50 kg, and the other a mass of 35 kg. Where should the third boy, whose mass is 25 kg, place himself so as to balance the seesaw?