Answer:
Explanation:
The tension in a cable is given by:
Where is the mass density of the cable and v is the speed of the cable's pulse. These values are defined as:
The pulse makes four trips down and back along the cable, so
Replacing (2) and (3) in (1), we calculate the tension in the cable:
Answer: 0.5 seconds or 2.625 seconds
Explanation:
At t = 0, The ball is 4 ft above the ground.
The height of the football varies with time in the following way:
s(t) = -16 t² + 50 t + 4
we need to find the time in which the height would of the football would be 25 ft:
⇒25 = -16 t² + 50 t + 4
we need to solve the quadratic equation:
⇒ 16 t² - 50 t + 21 = 0
⇒ t = 0.5 s or 2.625 s
Therefore, at t = 0.5 s or 2.625 s, the football would be 25 ft above the ground.
The mechanical energy of the system is sum of the potential and kinetic
energy of the system.
Response:
Mechanical energy, M.E. in the block and spring system can be presented as follows;
M.E. = Energy in the spring + Kinetic energy of the blocks + Energy done on friction
When the blocks are held at rest;
The mechanical energy in the block-spring system when the blocks are held at rest can be found as follows;
Energy in the spring = 0
Kinetic energy of the blocks = 0
Friction energy = 0
Therefore;
E1 for the block at rest = 0
E1 when the blocks come to rest again
Energy in the spring = > 0
Kinetic energy = 0
Energy of friction = 0
Therefore;
The mechanical energy of the block-spring system, E1, increases
When the blocks are held
Energy in the spring = 0
Energy done due to friction = 0
Potential energy of Block B = m·g·h
Kinetic energy of the blocks = 0
When the blocks come to rest again, we have;
Energy in the spring =
Energy received due to friction = 0
Potential energy of Block B = m·g·(h - y)
Where;
Which gives;
The energy in the spring-block-Earth system, E2, when initially held is more than the the energy when the blocks com to rest again.
Therefore, E2 decreases
The correct option is therefore;
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