A crate filled with food rests on a horizontal floor. Only gravity and the support force of the floor act on it, as shown by the vectors for weight W and normal force N.
1) The net force of the crate is
a) zero
b) greater than 0
2) The evidence for Numer one is...
A slight pull P is exerted on the crate, not enough to move it.
1) A force of friction f now acts which is ___ P.
a) less than
b) equal to
c) greater than
2) This type of friction is called _____ friction.
a) static
b) sliding or kinetic
c) rolling
3) The net force on this crate is...
a) zero
b) greater than zero
The pull on the crate is increased until the crate begins to move. It is pulled with pull P so that it moves with constant velocity across the floor.
1) Friction is ____ P.
a) less than
b) equal to
c) greater than
2) This type of friction is called _____ friction.
a) static
b) sliding or kinetic
c) rolling
3) Constant velocity means acceleration is...
a) zero
b) greater than zero
4) The net force on the crate is ____ zero.
a) less than
b) equal to
c) greater than
The pull P is further increased and is now greater than friction f.
1) The net force on the crate is ____ zero.
a) less than
b) equal to
c) greater than
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A crate filled with food rests on a horizontal floor. Only gravity and the support force of the floor act on it, as shown by the vectors for weight W and normal force N.
1) The net force of the crate is
a) zero<<<<<
b) greater than 0
2) The evidence for Numer one is...
>>>there are no acting forces
A slight pull P is exerted on the crate, not enough to move it.
1) A force of friction f now acts which is ___ P.
a) less than
b) equal to
c) greater than<<<<<<<<<
2) This type of friction is called _____ friction.
a) static
b) sliding or kinetic<<<<<<<<
c) rolling
3) The net force on this crate is...
a) zero
b) greater than zero<<<<<<<
The pull on the crate is increased until the crate begins to move. It is pulled with pull P so that it moves with constant velocity across the floor.
1) Friction is ____ P.
a) less than<<<<<<<<<
b) equal to
c) greater than
2) This type of friction is called _____ friction.
a) static
b) sliding or kinetic <<<<<<<<<
c) rolling
3) Constant velocity means acceleration is...
a) zero <<<<<<<<
b) greater than zero
4) The net force on the crate is ____ zero.
a) less than
b) equal to
c) greater than <<<<<<<<<<
The pull P is further increased and is now greater than friction f.
1) The net force on the crate is ____ zero.
a) less than
b) equal to
c) greater than<<<<<<<<<<
1) b) greater than 0
2) The evidence for number one is that the crate is not moving despite the pull being exerted on it. If the net force was zero, the crate would be in equilibrium and would not experience any acceleration, so it would remain at rest.
1) c) greater than
2) This type of friction is called static friction. It is the force that prevents the crate from moving even though a force is being applied to it. Static friction is greater than the force being applied because it needs to overcome the initial resistance to motion.
3) a) zero
The net force on this crate is zero because the crate is moving with constant velocity. This means that the force of friction is equal and opposite to the applied force, resulting in a net force of zero.
1) b) equal to
2) This type of friction is called sliding or kinetic friction. It is the force that opposes the motion of the crate as it slides across the floor. Once the crate is in motion, the force of kinetic friction is equal to the applied force.
3) a) zero
Constant velocity means there is no acceleration. Since acceleration is defined as the change in velocity over time, a constant velocity indicates zero acceleration.
4) a) less than
The net force on the crate is less than zero in this case because the applied force is greater than the force of friction. The crate will experience acceleration in the direction of the applied force.
1) The net force of the crate is b) greater than 0. To determine the net force acting on an object, we need to add up all the forces acting on it. In this case, the weight W (which is the force of gravity pulling the crate downward) and the normal force N (which is the support force exerted by the floor on the crate) are the only forces acting on the crate. Since these two forces are in opposite directions, they do not cancel each other out completely, and there is still a resultant force acting on the crate.
2) The evidence for number one is that the crate is at rest. When the net force on an object is zero, the object is either at rest or moving with constant velocity. In this case, since the crate is not moving, it implies that the net force on the crate is zero.
1) The force of friction f is a) less than P. As long as the crate is at rest and the pull P is not enough to move it, the force of static friction will be equal to and in the opposite direction of the pull P. It acts to prevent the crate from moving.
2) This type of friction is called a) static friction. Static friction is the frictional force that opposes the initiation of motion between two surfaces in contact. It acts when there is no relative motion between the surfaces.
3) The net force on this crate is a) zero. As mentioned earlier, when the crate is at rest, the forces acting on it (weight W, normal force N, and frictional force f) must add up to zero. This ensures that the crate remains in equilibrium.
1) Friction is b) equal to P. Once the pull P is increased to a certain threshold, the force of static friction reaches its maximum value and the crate starts to move. At this point, the force of static friction is equal to the magnitude of the pull P.
2) This type of friction is called b) sliding or kinetic friction. Sliding or kinetic friction is the frictional force that opposes the motion of two surfaces sliding past each other. It acts when there is relative motion between the surfaces.
3) Constant velocity means acceleration is a) zero. When an object is moving with a constant velocity, it means that its speed and direction are not changing. Since acceleration is the rate of change of velocity, a constant velocity implies zero acceleration.
4) The net force on the crate is b) equal to zero. When the crate is moving with constant velocity, the forces acting on it (weight W, normal force N, and frictional force f) must add up to zero. This ensures that the crate maintains its constant velocity.
1) The net force on the crate is c) greater than zero. When the pull P is increased and becomes greater than the force of friction f, the crate accelerates and starts moving with an increasing velocity. This acceleration is due to the net force acting on the crate, which is the difference between the pull force and the force of friction.