a block of wood with a mass of 2.33 kg is at rest on a frictionless pole. A .011 kg bullet is fired 722 m/s and is embedded with
1 answer:
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Answer:
T = 188.5 s, correct is C
Explanation:
This problem must be worked on using conservation of angular momentum. We define the system as formed by the fan and the paper, as the system is isolated, the moment is conserved
initial instant. Before the crash
L₀ = r m v₀ + I₀ w₀
the angular speed of the fan is zero w₀ = 0
final instant. After the crash
L_f = I₀ w + m r v
L₀ = L_f
m r v₀ = I₀ w + m r v
angular and linear velocity are related
v = r w
w = v / r
m r v₀ = I₀ v / r + m r v
m r v₀ = (I₀ / r + mr) v
v =
let's calculate
v =
v =
v = 0.02 m / s
To calculate the time of a complete revolution we can use the kinematics relations of uniform motion
v = x / T
T = x / v
the distance of a circle with radius r = 0.6 m
x = 2π r
we substitute
T = 2π r / v
let's calculate
T = 2π 0.6/0.02
T = 188.5 s
reduce
t = 188.5 s ( 1 min/60 s) = 3.13 min
correct is C
The work done on the ship is
Explanation:
The work done by a force on an object is given by:
where
F is the magnitude of the force
d is the displacement
is the angle between the direction of the force and of the displacement
In this problem, we have:
(force acting on the ship)
d = 3.00 km = 3000 m (displacement of the ship)
(because the force is horizontal, and the displacement is horizontal as well)
Therefore, the work done on the ship is
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1) The car overtakes the truck at a distance of 160 m far from the intersection.
2) The velocity of the car is 40 m/s
Explanation:
1)
The car is travelling with a constant acceleration starting from rest, so its position at time t (measured taking the intersection as the origin) is given by
where
is the acceleration
t is the time
On the other hand, the truck is travelling at a constant velocity, therefore its position at time t is given by
where
v = 20 m/s is the velocity of the truck
t is the time
The car overtakes the truck when the two positions are the same, so when
So, after a time of 8 seconds. Therefore, the distance covered by the car during this time is
So, the car overtakes the truck 160 m far from the intersection.
2)
The motion of the car is a uniformly accelerated motion, so the velocity of the car at time t is given by the suvat equation
where
v is the velocity at time t
u is the initial velocity
a is the acceleration
For the car in this problem, we have:
u = 0 (it starts from rest)
And we know that the car overtakes the truck when
t = 8 s
Substituting into the equation,
Learn more about accelerated motion:
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