Answer:
(A) The speed just as it left the ground is 30.25 m/s
(B) The maximum height of the rock is 46.69 m
Explanation:
Given;
weight of rock, w = mg = 20 N
speed of the rock at 14.8 m, u = 25 m/s
(a) Apply work energy theorem to find its speed just as it left the ground
work = Δ kinetic energy
F x d = ¹/₂mv² - ¹/₂mu²
mg x d = ¹/₂m(v² - u²)
g x d = ¹/₂(v² - u²)
gd = ¹/₂(v² - u²)
2gd = v² - u²
v² = 2gd + u²
v² = 2(9.8)(14.8) + (25)²
v² = 915.05
v = √915.05
v = 30.25 m/s
B) Use the work-energy theorem to find its maximum height
the initial velocity of the rock = 30.25 m/s
at maximum height, the final velocity = 0
- mg x H = ¹/₂mv² - ¹/₂mu²
- mg x H = ¹/₂m(0) - ¹/₂mu²
- mg x H = - ¹/₂mu²
2g x H = u²
H = u² / 2g
H = (30.25)² / 2(9.8)
H = 46.69 m
The Beams And Joints That Hold It .
Answer:
True
Explanation:
Given that Power whose unit is Watt equates to one joule of work per second. It implies that Power is directly proportional to the work done and inversely proportional to the time to do the work.
Therefore, in this case, the right answer to the question is that it is TRUE that the power is inversely proportional with time
Answer:
Refer to the attachment for solution (1).
<h3><u>Calculating time taken by it to stop (t) :</u></h3>
By using the second equation of motion,
→ v = u + at
- v denotes final velocity
- u denotes initial velocity
- t denotes time
- a denotes acceleration
→ 0 = 5 + (-5/6)t
→ 0 = 5 - (5/6)t
→ 0 + (5/6)t = 5
→ (5/6)t = 5
→ t = 5 ÷ (5/6)
→ t = 5 × (6/5)
→ t = 6 seconds
→ Time taken to stop = 6 seconds
The electrical equivalent of one horsepower is 746 watts in the International System of Units (SI), and the heat equivalent is 2,545 BTU (British Thermal Units) per hour. Another unit of power is the metric horsepower, which equals 4,500 kilogram-metres per minute (32,549 foot-pounds per minute), or 0.9863 horsepower.
