A brick is thrown from a wall that is 19.2 m above the ground and hits the ground 5.00 s later. What was the initial velocity of
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Answer:
Minimum work = 5060 J
Explanation:
Given:
Mass of the bucket (m) = 20.0 kg
Initial speed of the bucket (u) = 0 m/s
Final speed of the bucket (v) = 4.0 m/s
Displacement of the bucket (h) = 25.0 m
Let 'W' be the work done by the worker in lifting the bucket.
So, we know from work-energy theorem that, work done by a force is equal to the change in the mechanical energy of the system.
Change in mechanical energy is equal to the sum of change in potential energy and kinetic energy. Therefore,
Therefore, the work done by the worker in lifting the bucket is given as:
Now, plug in the values given and solve for 'W'. This gives,
Therefore, the minimum work that the worker did in lifting the bucket is 5060 J.
Answer
mass of the block A = 20 Kg
mass of block B = 10 Kg
acceleration of Block A = ?
acceleration of Block B = ?
Assuming the magnitude of force = 124 N
Applying newton's second law
F = 2 T
T = F/2
now, Tension in the string =
T = 124/2 = 62 N
Weight of the block A
W = m₁ g
W = 20 x 9.8 = 196 N
Weight of the block B
W = m₂ g
W = 10 x 9.8
W = 98 N
Weight of blocks is greater than force applied by the pulley so, the blocks will not move.
Hence, acceleration of the block A and B = 0 m/s²
If the Force magnitude is increased to 294 N
T = F/2 = 294/2 = 147 N
Since this Force is less than Weight A acceleration of the block A = 0 m/s².
For Block B
Tension is more than Weight hence block will move
Net Force = 147 - 98 = 49 N
acceleration =
a = 4.9 m/s²