A potato of mass 0.140 kg is tied to a string with length 2.65 m , and the other end of the string is tied to a rigid support. The potato is held straight out horizontally from the point of support, with the string pulled taut, and is then released.
a) What is the speed of the potato at the lowest point of its motion?
Take free fall acceleration to be g = 9.80 m/s2 .
b) What is the tension in the string at this point?
PHYSICS HELP?
2019-02-27 2:01 pm
回答 (2)
2019-02-27 3:00 pm
a)
Gain in K.E. = Loss in P.E.
(1/2) m v² = m g h
v = √(2 g h) = √(2 × 9.80 × 2.65) m/s
Speed at the lowest point = 7.21 m/s
b)
At the lowest point:
Total upward forces = Total downward forces
T = (mv²/r) + mg
T = (0.140 × 51.94 / 2.65) + 0.140 × 9.80 N
Tension in the string, T = 4.12 N
Gain in K.E. = Loss in P.E.
(1/2) m v² = m g h
v = √(2 g h) = √(2 × 9.80 × 2.65) m/s
Speed at the lowest point = 7.21 m/s
b)
At the lowest point:
Total upward forces = Total downward forces
T = (mv²/r) + mg
T = (0.140 × 51.94 / 2.65) + 0.140 × 9.80 N
Tension in the string, T = 4.12 N
2019-02-27 11:56 pm
The first step is to determine the horizontal vertical components of the force.
Horizontal = 16.8 * cos 26.1 ≈ 15.1 N
Vertical = 16.8 * sin 26.1 ≈ 7.39 N
Since he surface is frictionless, only the horizontal component of the force will do work on the block.
Work = 16.8 * cos 26.1 * 2.16 = 36.288 * cos 26.1
This is approximately 32.6 J. The normal force exerted by the table is equal to the sum of the vertical component of the force and the weight of the block.
Weight = 2.10 * 9.8 = 20.58 N
This is the force of gravity.
Normal force = 16.8 * sin 26.1 + 20.58
This is approximately 28 N.
d) Determine the magnitude of the net force on the block.
Since the two forces are perpendicular to each other, we need to use the Pythagorean Theorem to determine magnitude of the net force on the block.
F = √[(16.8 * cos 26.1)^2 * (16.8 * sin 26.1 + 20.58)^2]
This is approximately 31.8 N. I hope this is helpful for you.
Horizontal = 16.8 * cos 26.1 ≈ 15.1 N
Vertical = 16.8 * sin 26.1 ≈ 7.39 N
Since he surface is frictionless, only the horizontal component of the force will do work on the block.
Work = 16.8 * cos 26.1 * 2.16 = 36.288 * cos 26.1
This is approximately 32.6 J. The normal force exerted by the table is equal to the sum of the vertical component of the force and the weight of the block.
Weight = 2.10 * 9.8 = 20.58 N
This is the force of gravity.
Normal force = 16.8 * sin 26.1 + 20.58
This is approximately 28 N.
d) Determine the magnitude of the net force on the block.
Since the two forces are perpendicular to each other, we need to use the Pythagorean Theorem to determine magnitude of the net force on the block.
F = √[(16.8 * cos 26.1)^2 * (16.8 * sin 26.1 + 20.58)^2]
This is approximately 31.8 N. I hope this is helpful for you.
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