The work-energy principle states that an increase in the kinetic energy of a rigid body is caused by an equal amount of positive work done on the body by the resultant force acting on that body. Conversely, a decrease in kinetic energy is caused by an equal amount of negative work done by the resultant force.
B. Sound, because everything else sits still and sound waves move
Answer:
(a) 42 N
(b)36.7 N
Explanation:
Nomenclature
F= force test line (N)
W : fish weight (N)
Problem development
(a) Calculating of weight of the heaviest fish that can be pulled up vertically, when the line is reeled in at constant speed
We apply Newton's first law of equlibrio because the system moves at constant speed:
∑Fy =0
F-W= 0
42N -W =0
W = 42N
(b) Calculating of weight of the heaviest fish that can be pulled up vertically, when the line is reeled with an acceleration whose magnitude is 1.41 m/s²
We apply Newton's second law because the system moves at constant acceleration:
m= W/g , m= W/9.8 , m:fish mass , W: fish weight g:acceleration due to gravity
∑Fy =m*a
m= W/g , m= W/9.8 , m:fish mass , W: fish weight g:acceleration due to gravity
F-W= ( W/9.8 )*a
42-W= ( W/9.8 )*1.41
42= W+0.1439W
42=1.1439W
W= 42/1.1439
W= 36.7 N
The real advantage to hydrostatic weighing is that it gives one of the most accurate measurements of body fat.
The final velocity of the two pucks is -5 m/s
Explanation:
We can solve the problem by using the law of conservation of momentum.
In fact, in absence of external force, the total momentum of the two pucks before and after the collision must be conserved - so we can write:
where
is the mass of each puck
is the initial velocity of the 1st puck
is the initial velocity of the 2nd puck
v is the final velocity of the two pucks sticking together
Re-arranging the equation and solving for v, we find:
Learn more about momentum:
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