KNPE 153 Chapter Notes - Chapter 5: Median Plane, Net Force, Weight Plate

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ultramarinemole832

2 Dec 2016

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Its location is not marked on an object: useful concept for analysis of human movement. It is the point at which the entire mass or weight of the body may be considered to be concentrated. The force of gravity acts downward through this point. If the net external force acts on a body, the acceleration caused by this net force is the acceleration of the center of gravity. If no external forces act on an object, the center of gravity does not accelerate. When interpreting and applying newton"s laws of motion, it is the center of gravity of a body whose motions are ruled by these laws. Locating the center of gravity of an object: The sum of the moments of force created by each of the elemental weights equals the moment of force created by the total weight stacked at the center-of-gravity location. W = the weight of one element r = the moment arm of an individual element.

Related Questions

1. Under which circumstance does the center of gravity of an object coincide with the center of mass?

a. when the mass is uniformly distributed

b. when the center of mass is located inside the object

c. when the value of the gravitational acceleration is the same throughout the object.

2. If the net force and the net torque on a moving object are both zero, can the object be in static equilibrium?

a. yes

b. No

3. If an object is to be in equilibrium, which of the following must be true of the linear momentum of its center of mass?

a. must be increasing at a steady rate
b. must be decreasing at a steady rate
c. must be constant

burgundycicada286

1. If an object is rotating clockwise, this corresponds to a _____ angular velocity:

a- negative

b- positive

2. The angular displacement of a rotating object is measured in

a- degrees per second

b- degrees

c- radians

3. Which factor does the torque on an object NOT depend on?

a- the angle at which the force is applied

b- the object's angular velocity
c- the magnitude of the applied force

4. A net torque applied to an object causes __________.

a- the object to rotate at a constant rate
b- a linear acceleration of the object
c- the moment of inertia of the object to change
d- the angular velocity of the object to change

5. For an extended object, the weight force can be considered to act at which point?

a- At the center of gravity of the object
b- At the center of the object
c- At end of the object closest to the ground
d- At the end of the object farthest away from the ground

6. Moment of inertia is __________.

a- the rotational equivalent of mass
b- the point at which all forces appear to act
c- the time at which inertia occurs

peachgrasshopper627

1) An object is moving with constant velocity. Which of the following statements is true?
a) A constant force is being applied in the direction of motion.
b) A constant force is being applied in the direction opposite of motion.
c) There are no forces acting on the object.
d) The net force on the object is zero.
e) There is no frictional force acting on the object.

2) You apply the same force to two objects. Object 1 has mass M and object 2 has mass 5M. The acceleration is
a) ten times that of object 1 b) five times that of object 1
c) the same as that of object 1 d) 1/5 as that of object 1

3) An object of weight W is in free-fall close to the surface of Earth. What is the force that the object exerts on Earth?
a) a force greater than W b) a force less than W
c) a force equal to W d) no force at all

4) A parking crate slides down an inclined ramp at constant velocity. Thus we can deduce that _
a) a frictional force is acting on it
b) a net downward force is acting on it
c) a net upward force is acting on it
d) it is not acted on by appreciable normal force
e) it is not acted on by appreciable gravitational force

5) A person applies a constant force of 20N to a rock of mass 1000kg for a total of 20 seconds. What is the work done by this person if the person does not move at all by this applied force?
a) 1000J b) 2000J c) 20,000J d) 0J e) 400J

6) If the net work done on an object is positive, then the object's kinetic energy.
a) decreases b) remains the same c) increases d) is zero

7) You throw a ball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down.
a) Work is + on the way up and + on the way down
b) Work is + on the way up and - on the way down
c) Work is - on the way up and + on the way down
d) Work is - on the way up and - on the way down

lavenderbat941

KNPE 153 Chapter Notes - Chapter 5: Median Plane, Net Force, Weight Plate

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