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Gravity
Terms in this set (81)
Force Couple:
Moment of a force couple does not depend on the point of force application. True or False?
true
Force-velocity:
If a 100 N force (F) was applied for 2 s (t) to a 20-kg (m) object initially moving at 2 m/s (v), what would be the object's final velocity (v)?
12 m/s
Inertia:
Which of the following best describes inertia?
A measure of an object's resistance to change motion
Friction:
Cleated shoes are used to improve the coefficient of friction and get better traction on the playing surface. Researchers have suggested that a potential (mu,s) provides sufficient friction for sporting purposes. What are the potential consequences of having very high or very low friction in shoe soles?
Baseball:
During throwing a baseball, a pitcher can throw the ball in such a way that the ball curves horizontally. Given this observation, which of the following conclusions is correct?
a horizontal force causes the horizontal change in motion
Lift and Drag Force:
Compute the lift and drag forces applied to the box in the figure shown below
Lift force = 73.1 N
Drag force = 68.2 N
Net Force:
Compute the net vertical force on the skater. (Upward is positive)
60 N
Vertical Acceleration:
What is the vertical acceleration of the center-of-mass of the skater?
1.21 m/s^2
Force Couple:
Force couples are omnipresent in ergonomic design. Which of the following is not an example of a force-couple? Click on the image
Momentum Conservation:
In the video you just saw , Lebron James weighs 114 kg and Tony Parker weighs 82 kg. If James was running towards Parker with a velocity of 8 m/s, at what speed would Parker have to run towards James so that they both come to a complete standstill after a midair collision? (Hint: Momentum conserved in the absence of external force). NO CORRECTNESS POINTS
11.1 m/s
Frictional force:
The skater is gliding along the ice and the coefficient of dynamic friction between the blade and ice is (mu,d)= 0.06. Compute the frictional force (F,f) .
32.7 N
Skater mass:
Compute the mass of the skater.
49.4 kg
Air-drag:
Patrick ran a 5k in 20 minutes on a flat course and in a straight line. Determine the drag force that was acting against his motion. Drag coefficient of 0.6, frontal area of 1.5 m^2 and air-density of 1 kg/m^3 . The headwind speed was 1 m/s (hint: headwind is acting opposite to the direction of running).
12.01 N
Centripetal Force:
The athlete performs a hammer throw. Calculate the centripetal force on the ball as it is being spun. (Radius: 1m; mass of the ball: 2kg; tangential speed of ball: 3 m/s).
18 N
COP and Gait:
Which aspect of gait would be hardest to detect using center of pressure measurements? NO CORRECTNESS POINTS
knee flexion
Impulse take-off velocity calculation:
Calculate the takeoff velocity for a jump based on the following hypothetical vertical ground reaction force data? The jumper's mass is 71.4 kg. NO CORRECTNESS POINTS.
1.4 m/s
Energy conservation:
A diver (mass 60 kg) dives from a 10-m platform. What is her potential and kinetic energy at a height of 4 meters from the water?
PE = 2,354 J
KE = 3,532 J
FBD:
Consider the following FBD. Using static analysis, solve for the horizontal and vertical forces of C that will maintain the system in equilibrium. (hint: C is not a horizontal force). A=50 N; B=30 N; W=100 N.
horizontal = -64.5 N
vertical = 96.2 N
Football Player:
A 200 kg football player is running toward another player at 12 m/s. How much average force needs to be applied over 2.0 seconds to bring him to a stop?
1,200 N
Power:
If an individual's leg exerts a force of 10 N as it moves 0.6 m in 0.3 seconds, what is the power generated by the leg?
20 W
Impulse of a Force:
A force increases from 0 to 3.0 N linearly in 3 seconds, and then decreases from 3.0 N to 0 N in 4 seconds (also linearly). What is the impulse generated by the force?
10.5 Ns
Toe-off velocity:
A runner's horizontal velocity is 4.0 m/s and their mass is 60 kg at heel-strike. The anterior-posterior ground reaction forces are shown in the figure below. What is their horizontal velocity at toe-off?
4.04 m/s
Impulse Take-off
An athlete weighs 81.6 kg. He is standing on a force plate and then produce the following vertical ground reaction force before take-off. Assuming that their initial velocity is 0, compute how high they would jump after take-off? In other words, how high would their center-of-mass move?
4.9 cm
Stance phase running:
Which equation is appropriate for determining the vertical ground reaction force during the stance phase of running?
F,z = m (a,z - g)
CMJ:
During a countermovement jump, there is a period of time where forces acting on the person from the ground are less than body weight (see figure below). Which of the following statements best explains this observation?
velocity is increasing in the negative direction
Object in air:
When an object is thrown in the air, which of the following forces does not act on the object?
centripetal force
centripetal force:
What would be the centripetal force of an object (m = 2 kg) rotating about a radius of 0.5 m at 1.5 rad/s?
2.25 N
Drop jumps:
Consider an experiment where a subject lands during two conditions from a height of 0.2 m. During the first landing condition, the subject lands "stiffly" (e.g., very little knee flexion). During the second landing condition, the subject lands "softly" (e.g., lots of knee flexion). During the soft landing, the peak vertical forces are less than during the stiff landing. Which of the following statements best explains this observation?
the length of time a force is applied is increased during the soft landing compared to the stiff landing
Spring:
What would be the force exerted by a spring with a stiffness of 100 N/m that was compressed 0.02 m?
2.0 N
Friction:
During running, the dynamic coefficient of friction can be calculated using which formula (F,y = anterior/posterior; F,x = medial/lateral; F,z = vertical force components)?
mu = F,y / F,z
Gait Cycle:
The figure shows when different muscle groups are active during the gait cycle. During the late swing phase, the hamstrings are active and lengthening (highly activity) and also during stance, when contact loads are present (moderately active). If you were walking briskly with a heavy backpack load, in which phase of the gait cycle are the hamstrings most vulnerable to getting injured?
late swing phase
COM:
During the support phase of running, if the vertical ground reaction force was 1,000 N for a runner (mass = 80 kg), what would be the acceleration of the center of mass?
2.7 m/s^2
KE:
When dropping a ball (mass = 10 kg) from a height of 2 m, what will be the kinetic energy of the ball at the point of impact with the ground?
196 J
Types of angles:
Given the stick figure, which of the angles classifies as a distal end absolute angle?
Absolute Angles:
Calculate the absolute angle of theta, thigh
Relative Angle:
Calculate the knee flexion angle theta, knee-flexion
Angular Velocity Pitcher:
During a softball pitch, the pitcher's arm goes through 120° of angular displacement over 0.25 s. What is the average angular velocity in °/sec?
480
Angular Position:
If angular velocity (ω) was 10°/s for 1.5 s (delta,t), what would be the final angular position (θf) if the initial angular position (θi) was 5°?
20 degrees
Absolute Angle 2:
Compute the absolute leg angle in the image shown below (in degrees)
Relative Angle 2:
Compute the knee flexion angle in the figure below (in degrees)
Slope:
If the slope of angular velocity versus time plot is zero, then which of the following statements must always be true?
Angular acceleration is zero
Angular velocity:
During the latter portion of the swing phase of a walking stride, the knee is extended from 65° to 5° over a time period of 0.12 s. What is the angular velocity?
-500 deg/s
Angular acceleration:
If angular acceleration is negative, which of the following statements could be true?
angular velocity is positive and decreasing
angular velocity is negative and decreasing
Angular displacement:
During an activity, if the initial angle (theta,i) of a segment was 180°, and the final angle (theta,f) was 100°, what was the angular displacement?
-80 deg
Arc Length:
During the swing of a bat through an arc of 2 rad (114.6°), what would be the linear distance that the tip of the bat would have traveled if the radius of rotation was 1.5 m?
3 m
Hammer throw:
During a hammer throw, an athlete swings a mass about an axis of rotation. What would be the centripetal acceleration in m/s^2 if the radius of rotation was 1.25 m and angular velocity was 7 rad/s?
61.25
Knee extension:
During the latter portion of the swing phase of a walking stride, the knee is extended from 65° to 5° over a time period of 0.12 s. What is the angular velocity in deg/s?
-500
Angular Velocity:
What would have been the initial angular velocity (w,i) in deg/s if angular acceleration (a) was 10°/s^2 for 1.5 s (delta t) and final angular velocity (w,f) was 100°/s?
85
Tangential Acceleration:
What would be the tangential linear acceleration if an object's angular velocity was increased from 229.18 to 401.07 /s in 1.2 s about a 1.5-m radius of rotation?
3.75 m/s^2
Discus Throw:
The figure below shows a discus throw in which an athlete rotates at high angular velocities before releasing the discus. The angular velocity of the athlete at the point of release is 25 rad/sec and the radius of release is 1.4 m (see figure). The release angle is θ=60° and height of release is h = 2.2 m (see figure). Find the horizontal displacement (R) of the discus put when it lands. The equation for range is also given below. Here is the initial velocity and h is the height of release.
109.4 m
Angle Type:
Identify the two angles in the picture below.
A is relative
B is absolute
Scoliosis:
Why would scoliosis affect gait kinematics? (Multiple correct answers)
Knee Osteoarthritis:
Patients with knee osteoarthritis exhibit reduced knee flexion during the stance phase of the gait cycle (see figure below). The knee behaves like a linear spring during the weight acceptance phase of the stance phase. Reduced knee flexion would __ (Multiple correct answers)
Angular velocity and acceleration:
Compute the missing (in grey) angular velocity and acceleration for the thigh movement as shown in the table below.
-89 deg/s
5400 deg/s^2
Linear angular relationship:
A hockey player is rotating his stick at 1600/sec. If the blade of the stick is located 1.4 meters from the axis of rotation, what is the linear speed of the blade right before impact with the puck?
39.1 m/s
Radial acceleration:
These two bicyclists are racing and enter a slippery corner with a tangential velocity of 30 m/s. Which cyclist experiences the greater radial acceleration? Click on the cyclist.
Vectors:
A vector is a parameter that is described by ⋯ and ⋯ .
magnitude, direction
Vector Decomposition:
Compute the values of A and B respectively.
Sailboat Velocity:
A sailboat has coordinates (100 m, 185 m) at t0=0.0 s. Three minutes later its position is (140 m, 218 m). What is its average velocity in the x direction?
0.22 m/s
Sailboat Velocity 2:
A sailboat has coordinates (100 m, 185 m) at t0=0.0 s. Three minutes later its position is (140 m, 218 m). What is its average velocity in the y direction?
0.18 m/s
Acceleration:
Given an acceleration of -6 m/s^2, which of the following statements is always true?
Acceleration magnitude:
The magnitude of acceleration would be greatest for which of the following situations?
v,i = 4 m/s
v,f = 8 m/s
dt = 1 s
Negative Acceleration:
During the end of a 100-m race, a runner's acceleration is negative. Which statement accurately interprets this observation?
The runner is slowing down while moving in the positive direction.
Acceleration Decomposition:
Compute the horizontal component of the acceleration a,x in m/s^2?
10.18
Acceleration Decomposition2;
Compute the vertical component of the acceleration a,y in m/s^2?
6.36
Frame rate velocity calculation:
During running 100 m, a runner runs from the 20- to 30-m mark in 60 frames of a video record. If the video camera recorded data at 50 fps, how fast was she running during this interval?
8.3 m/s
Final velocity:
A soccer ball is rolling with a constant acceleration (a) of -0.5 m/s^2. At t,i = 0 s, the ball has an instantaneous velocity of 6 m/s (v,i). After 3 s (t,f) of rolling, what would be the velocity (v,f) of the ball?
4.5 m/s
First Central difference method:
Calculate the velocity at frame 3 using the first central difference method, given the following data set:
3.59 m/s
Slope:
The slope of a vertical position versus time plot is equivalent to which kinematic parameter?
velocity
Relationship - velocity and acceleration:
Velocity information can be calculated from acceleration data through the process of ⋯
integration
Riemann sum
Integrate acceleration:
An object starts from rest, vi=0, and undergoes acceleration as shown in the figure below. What is its final velocity, vf?
60
Final velocity:
What would be the final velocity (vf) of a projectile dropped from an initial height of 2.5 m (si) and a final height of 0 m (sf) with zero initial velocity (vi)? (Up is positive)
-7 m/s
velocity magnitude:
What would be the magnitude of the resultant velocity of a projectile if the horizontal velocity was 3 m/s and if the vertical velocity was 4 m/s?
5 m/s
height projectile:
Calculate the apex of a projectile relative to the ground if the initial vertical velocity of the object was 3 m/s and the height of release was 1 m above the ground.
1.46
Integrate acceleration to get velocity:
An object starts at rest, v= 0 m/s, and undergoes acceleration in the x-direction as shown in the figure below. What is its final velocity, v, at the end of 10 s in the x-direction?
51
Range of projectile:
If v,0= 20 m/s and θ=52°, find the range of the projectile.
39.6
Sprint:
Two runners compete in a 100 m run. Runner A's stride length is 1.25 meters and stride rate is 4.0 s-1. Runner B's stride length is 1.5 and stride rate is 3.5 s-1. Who wins?
B
Rectangular to polar coordinates:
Convert the rectangular coordinates of (100, 200) to polar coordinates
223.6, 63.4
Long-jumper:
At take-off, the horizontal and vertical velocity of a long jumper are 7 and 5.2 m/s, respectively. What is her angle of take off and how far does she jump?
36 deg
7.43 m
Baseball:
A baseball outfielder can throw the baseball to a maximum horizontal distance of 100 m. How much vertically high above the ground can the outfielder throw the same ball?
50 m
Moving average and integrated EMG:
The following set of numbers represents a hypothetical EMG signal [2,-3, 4, 0, -1, -6]. Which one of the following sets represents a rectified, 3-point moving average, and integrated EMG signal?
[3, 5.33, 7, 9.33]
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