Biomechanics final true/false questions

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T/F: since force is a vector, it only has a magnitude

False; it has a direction too

T/F: As long as the distance between your center of mass and the earth's center of mass is constant, so is gravity

True

T/F: Assuming your mass is constant when you sleep, you can decrease pressure by lying on your back versus your side

True

T/F: The center of pressure under your left foot when standing may be in location of zero pressure

True

T/F: When a force vector is resolved into its orthogonal components, the magnitude of the resultant vector is always larger than any of the components

True

T/F: You performed vertical jumps on a force platform two times. The time you generate greater vertical impulse was the time you jumped higher

True

(T/F) A shuffleboard puck slows down as it slides on the floor because of its mass

false

A force couple produces only rotation without translation because the two torques act in the same direction.

false

A pole vaulter in flight has only kinetic energy

false

A torque and a moment of force do not have the same meaning.

false

By convention, clockwise torques are considered to be positive.

false

During the stance phase of running, positive power at the hip, knee, and ankle joints indicates eccentric contractions.

false

If mechanical work = zero, we can assume that the muscle contraction is eccentric

false

Moment of inertia about an axis always passes through the center of mass of a segment.

false

Only forces are shown in a free body diagram.

false

Person A, who has half the mass of Person B, will be able to cause the same impulse on an object as Person B if she moves with twice the velocity of Person B.

false

Potential energy is proportional to an object's mass and inversely proportional to its height from the ground.

false

Resistance of a thigh to rotate about its longitudinal axis is greater than its resistance to rotate about a mediolateral axis.

false

Second-class levers require large effort forces relative to resistant forces and maximize the speed of movement.

false

T/F: Backspin imparted on a golf ball is an example of the Magnus effect, in which low pressure on the bottom and high pressure on the top result in the ball lifting upward

false

T/F: Frictional force depends on the contact area, and the coefficient of friction between the two objects of interest

false

T/F: The normal force is always directed anteroposteriorly

false

The center of mass and the center of gravity are the same.

false

The direction of the torque vector changes if the force vector rotates around the axis of rotation.

false

The final acceleration in the golf club during the downswing is attributed to the moment of inertia decreasing as the club center of mass gets closer to the axis of rotation.

false

The largest moment of inertia of a segment is the one that passes through the center of mass.

false

The sum of torques about the center of mass of an object always equals zero

false

The total energy in a system can be created but not destroyed

false

To work your deltoids more during a lateral arm raise, bend your elbows slightly, bringing the weight closer to your trunk.

false

concurrent forces do not coincide at the same point

false

the strongest lever is a third class lever

false

You multiply joint moment with segment velocity to get joint power

false (this was ch 12 #14 he said he would change it to this bc original does not make sense)

T/F: During walking, the magnitude of GRF from highest to lowest is vertical, mediolateral, and anteroposterior

false; it is from high to low: vertical, anteroposterior, then mediolateral

T/F: an objects mass is not a good estimate of its inertia

false; they are related

A dynamic analysis is always conducted from the most proximal joint to the most distal joint.

true

A force has to be applied over some time interval for an impulse to be generated

true

A force has to be applied over some time interval for an impulse to be generated.

true

A positive net moment indicates that angular acceleration is occurring

true

A rigid link model is illustrated in a free body diagram.

true

A static analysis is useful in a materials handling task.

true

An MA > 1 indicates the effort arm exceeds the resistance arm, which magnifies the moment created by the effort force.

true

Angular momentum increases if moment of inertia increases and decreases when angular velocity decreases.

true

Decreasing moment of inertia by going from a laid out to tucked body position when doing a backflip allows one to rotate quicker.

true

For a system to be in equilibrium, all forces and torques must equal zero

true

In a dynamic analysis, the linear and angular accelerations are nonzero

true

In a static analysis, the linear acceleration is constant.

true

Internal work may be either positive or negative

true

Mechanical work can be equated with energy expenditure

true

Once a gymnast leaves the vault, angular momentum remains constant while airborne if air resistance is neglected.

true

Rotational kinetic energy of the foot is more influenced by the foot's angular velocity than its moment of inertia.

true

T/F: An object in motion will not stop unless some external force acts on it

true

T/F: Force is a vector

true

T/F: Gravity and friction are examples of external forces

true

T/F: High frictional forces on a surface can be a trip hazard for someone walking on that surface.

true

T/F: If a 100 N force is applied to lift an object with a mass of 10 kg, that object will be accelerate upward

true

T/F: Laminar flow is most likely to occur when the object passing through the fluid is small, has a smooth surface, and is moving slowly

true

T/F: Only the force component tangential to the rim of a wheelchair causes propulsion

true

T/F: The amount of energy transmitted from you to the water when swimming is proportional to the disturbance of the water

true

T/F: The center of pressure can distinguish between runners who pronate versus those who do not.

true

T/F: Two pushing and pulling forces acting on the same point at the same time can be added together and represented as one resultant force

true

T/F: When you are standing still, the sum of all of the external forces acting on your body always equals zero

true

T/F: With a similar swing speed, a longer golf club will result in a greater tangential velocity

true

T/F: while a force can pull or push an object, your muscles can only technically pull, or create tensile forces

true

The inertial force in a dynamics analysis is the product of the moment of inertia and the angular acceleration.

true

The moment arm is always measured from the point of application of the force to the axis of rotation.

true

The moment of inertia about an axis through the center of mass is less than the moment of inertia about any other perpendicular axis running through any other point on the segment.

true

The only force creating a moment about the shoulder when an arm is held out to the side is the weight of the entire arm.

true

Third-class levers, where the effort and resisting forces are on the same side of the fulcrum, are most prominent in the body.

true

To balance a first-class lever, the moments at both ends must be equal.

true

To determine the net moment acting at the ankle joint, all moments acting on the system must be evaluated.

true

Total body angular momentum can be increased during a dive by forcefully swinging the arms downward.

true

When an ice skater is spinning, to stop they increase the moment of inertia.

true

You performed vertical jumps on a force platform two times. The time you generated greater vertical impulse was the time you jumped higher

true

if the center of mass is not elevated during walking, no external work is done

true

if the moment arm is greater than the resistance arm, the lever is a second-class lever.

true


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