) If you jumped from the same height into water as opposed to onto concrete, it would take
a greater impulse when landing on concrete to reduce your
... [Show More] speed to zero velocity
assuming you have the same posture at impact in each case
a.) True (NOT THIS) (From Rafael’s pictures)
b.) False (Correct)
2.) Typically, in which part of a 100m race would expect to find the greatest acceleration?
a.) End (NOT This) (From Rafael’s pictures)
b.) Middle
c.) Beginning (Correct)
3.) After successfully clearing the bar during the pole vault, the vaulter falls to the landing
cushion while trying to calculate the impending impulse which will break his fall. If his
momentum is -980 kg*m/s and he has a velocity of -12.5 m/s just prior to landing, what
is the average net force that the vaulter experiences after hitting the landing mat if it takes
0.5 secs to slow down to zero velocity?
a.) -3161.3 N
b.) +1960.0 N (Correct)
c.) +3156.4 N
d.) -1960.0 N (NOT This) (From Rafael’s pictures)
e.) +4005.5 N
Work:
MB + Impulse = MA
-980 kg.m/s + F (0.5s) = 0
+980 kg.m/s +980 kg.m/s
=
𝐹 (0.5𝑠)
(0.5𝑠)
980 𝑘𝑔.𝑚/𝑠
0.5 𝑠
F = +1960 N
4.) The lever system formed by the plantar flexor muscles pulling up on the back of the
calcaneus bone to create plantar flexion of the ankle joint is:
a.) First class
b.) Fourth class
c.) Third class
d.) Second class (Correct) (From Rafael’s pictures)
5.) The stabilizing component of a resultant muscle force is always parallel to the moving
bone on which the muscle inserts and is directed towards the joint center
a.) True (Correct) (From Rafael’s pictures)
b.) False
6.) A golfer taking part in a longest drive competition swings at the ball with all his might,
generating a linear velocity of 51 m/s at the moment of impact. If the radius of rotation
(length of the club and arms combined, measured from the axis of rotation) is 1.7m, what
is the angular velocity of the club head at impact?
a.) 42.5 rad/s
b.) 46.2 rad/s
c.) 86.7 rad/s
d.) 30 rad/s (Correct) (From Rafael’s pictures)
Work:
v = r ω
51 m/s = (1.7m)(ω)
=
51 𝑚/𝑠
1.7
1.7
1.7
ω = 30 rad/s
7.) A diver of mass 90kg enters the water at a velocity of -10 m/s. What is the impulse
required from the water to slow the diver to zero velocity?
a.) +900 N*s
b.) Not enough information
c.) +9 N*s
d.) -9 N*s
e.) -900 N*s (NOT This) (From Rafael’s pictures)
Work:
MB + Impulse = MA
(90kg x -10m/s) + Impulse = 0
-900kg + Impulse = 0
Impulse = +900 N*s
8.) During the execution of a hammer throw, which of the following ceases to exist on the
hammer/hammer thrower system at the instant of release?
a.) Centripetal force
b.) Centrifugal force
c.) Both of these (Correct) (From Rafael’s picture)
d.) Neither of these (NOT THIS) (From Rafael’s pictures)
9.) Typically, when increasing running velocity from fast to maximum speeds, the rate of
change of stride rate is usually greater than the rate of change of stride length
a.) True (Correct)
b.) False
10.) Torque is the angular analogue of
a.) Moment of inertia
b.) Momentum (NOT THIS) (From Rafael’s pictures)
c.) Force (Correct) -Pg. 482 pdf book
d.) Radius of gyration
e.) Impulse
11.) A person weighs -800N and is traveling downwards in an elevator whilst stood on a
bathroom scale (as one does!). The person notices that the scale doesn’t always read
bodyweight. When arriving at the bottom, the scale reads 840N. If the person has a mass
of 81.5kg, what is the acceleration of the elevator?
a.) +0.49 m/s² (Correct)
b.) -0.49 m/s²
c.) -20.12 m/s²
d.) Zero
e.) +20.12 m/s²
Work:
m = -800 N / 9.81 m/s^2 = 81.55 Kg
av = (840 N-800 N) / 81.55 Kg
av = 0.49 m/s^2
12.) What variable has the units kg*m²?
a.) Linear impulse
b.) Moment of inertia (Correct) -Lec. Angular Kinetics, slide 3 [Show Less]