Kinesiology 2241A/B Lecture Notes - Lecture 8: Vestibular System, Virtual Reality, Proprioception

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greengnu716

25 Mar 2018

School

Western University

Department

Kinesiology

Course

Kinesiology 2241A/B

Professor

Thomas Richard Jenkyn

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Document Summary

Equilibrium all forces and torques add to zero: you are always in equilibrium, and it has nothing to do with stability. Inertial forces act to oppose any accelerations of the center of mass: these are the for(cid:272)es that you (cid:862)feel(cid:863) (cid:449)he(cid:374) you are perfor(cid:373)i(cid:374)g a task (cid:449)ith acceleration. For static equilibrium the line of action of gravity acting on your center of mass will project onto your base of support: base of support the region between the edges of the points of contact. The larger the region the more stable: when standing it is the length of support. If the gravity line of action projects through the base of support then the system is stable and in static equilibrium. If you are highly stable, you lack mobility. If you are highly mobile, you lack stability. Posture maintaining upright postion: at ankles knees hips and spine extensor muscles maintain posture (anti-gravity muscles)

Related Questions

Part A

An object cannot remain at rest unless which of the following holds?

The net force acting on it is zero.

The net force acting on it is constant and nonzero.

There are no forces at all acting on it.

There is only one force acting on it.

Part B

If a block is moving to the left at a constant velocity, what can conclude?

There is exactly one force applied to the block.

The net force applied to the block is directed to the left.

The net force applied to the block is zero.

There must be no forces at all applied to the block.

Part C

A block of mass 2kg is acted upon by two forces: 3N (directed to the left) and 4N (directed to the right). What can you say about the block's motion?

It must be moving to the left.

It must be moving to the right.

It must be at rest.

It could be moving to the left, moving to the right, or be instantaneously at rest.

Part D

A massive block is being pulled along a horizontal frictionless surface by a constant horizontal force. The block must be __________.

continuously changing direction

moving at a constant velocity

moving with a constant nonzero acceleration

moving with continuously increasing acceleration

amethystraven1

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

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Kinesiology 2241A/B Lecture Notes - Lecture 8: Vestibular System, Virtual Reality, Proprioception

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