An electric bell is placed inside a transparent glass jar. The bell can be turned on and off using a switch on the outside of th
e jar. A vacuum is created inside the jar by sucking out the air. Then the bell is rung using the switch. What will we see and hear?
A) We’ll see the bell move, but we won’t hear it ring.
B) We won’t see the bell move, but we’ll hear it ring.
C) We’ll see the bell move and hear it ring.
D) We won’t see the bell move or hear it ring.
E) We’ll see the sound waves exit the vacuum pump.
A) We’ll see the bell move, but we won’t hear it ring.
B) We won’t see the bell move, but we’ll hear it ring.
C) We’ll see the bell move and hear it ring.
D) We won’t see the bell move or hear it ring.
E) We’ll see the sound waves exit the vacuum pump.
2 answers:
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Answer:
6.32 m/s 18.43° northeast
Explanation:
We express the velocity of hawk as:
We consider positive x towards east and positive y due north. So the magnitude is simply the square root of the square components:
≈
And the angle with respect to the east should be with:
Answer:
A) 1000 joules
Explanation:
In general work is given by the equation:
(1)
A) With the displacement and
the force applied, because the force and the displacement are parallel (the crate is pushed horizontally)
is simply
, and because the path is a straight line and the force is constant work is:
(2),
B) The work-energy theorem says that the total work on a body is equal to the change on kinetic energy:
(3)
The total work on the crate is the work done by the push and plus the work of the friction (4) , as (A) because forces are parallel to the displacement
(5) and
(6), the due friction always has negative sign because is opposite to the displacement, using (6), (5) and (4) on (3):
(3)
C) The energy is lost by friction, so the amount of energy turned into heat is the work the friction does:
(3)