Answer:
59.4 meters
Explanation:
The correct question statement is :
A floor polisher has a rotating disk that has a 15-cm radius. The disk rotates at a constant angular velocity of 1.4 rev/s and is covered with a soft material that does the polishing. An operator holds the polisher in one place for 4.5 s, in order to buff an especially scuff ed area of the floor. How far (in meters) does a spot on the outer edge of the disk move during this time?
Solution:
We know for a circle of radius r and θ angle by an arc of length S at the center,
S=rθ
This gives
θ=S/r
also we know angular velocity
ω=θ/t where t is time
or
θ=ωt
and we know
1 revolution =2π radians
From this we have
angular velocity ω = 1.4 revolutions per sec = 1.4×2π radians /sec = 1.4×3.14×2×= 8.8 radians / sec
Putting values of ω and time t in
θ=ωt
we have
θ= 8.8 rad / sec × 4.5 sec
θ= 396 radians
We are given radius r = 15 cm = 15 ×0.01 m=0.15 m (because 1 m= 100 cm and hence, 1 cm = 0.01 m)
put this value of θ and r in
S=rθ
we have
S= 396 radians ×0.15 m=59.4 m
Answer:
It takes her 3.409 seconds to make a full stop.
Explanation:
The time it takes to make a full stop can be determined by the equation of velocity for a Uniformly Accelerated Rectilinear Motion:
(1)
Where 
is the final velocity, 
is the initial velocity, a is the acceleration and t is the time.
Equation (1) can be rewritten in terms of t:
(2)
For this particular case the final velocity will be equal to zero (
):
So it takes her 3.409 seconds to make a full stop.
Answer:
The pressure remains the same.
F = P * A the amount of force transmitted would double if only the input area is changed. Pressure is the same at all points in the system.
Answer:
The bird has 20,000 times higher kinetic energy than the mosquito.
Explanation:
The formula for kinetic energy shows that the amount of energy is proportional to the mass:
The velocity of both objects being the same, the mass is the determiner. The ratio of the kinetic energy of the bird and the mosquito then becomes the ratio of their masses, i.e., 0.02kg/0.00001kg. The bird's energy is 20,000 times higher than that of the mosquito. This proportion becomes more believable if you imagine the event of a distracted errant bird colliding with your head, versus a confused mosquito colliding with your head.
