Answer:
answer a) 2
Explanation:
Assuming stationary state, following Fourier's law:
Q = A*k* dT/dL
where Q= heat flow , A= cross sectional area, dT/dL= temperature gradient along the bar
if the cross sectional area is doubled , then the gradient is the same ( since the heat sources do not change in temperature or position , and the length of the bar is the same). Since the gradient is same , the temperature is the same under stationary conditions , then we can assume k remains constant in the cross section.Therefore
Q₁= A₁*k* dT/dL
Q₂= A₂*k* dT/dL
dividing both equations
Q₂ / Q₁ = A₂/A₁ = 2
then the correct answer is a)
Note:
Since the cross sectional area is doubled, then heat loss to the surroundings will be
Q loss= h* A exposed * ΔT
then
Q loss₂ / Q loss ₁ = A exposed ₂/ A exposed ₁
for a circular cross section or a squared cross section
A exposed ₂/ A exposed ₁ = √2
then
Q loss₂ / Q loss ₁ = √2
therefore we did not take into account the increase in heat loss due to the increased in exposed area to the environment
<h3>
Answer:</h3>
24860 N
<h3>
Explanation:</h3>
From the question;
- Mechanical advantage is 0.0893
- Output force is 2220 Newtons
We are required to determine the input force;
- We know that mechanical advantage is the ratio of output force to input force.
- That is; M.A. = Output force ÷ Input force
- Rearranging the formula;
Input force = Output force ÷ M.A.
Therefore;
Input force = 2220 N ÷ 0.0893
= 24860 N
Hence, the input force is 24860 N
Answer:
The velocity with which the ball strikes the ground = -5.7 m/s
Explanation:
To find the velocity with which the tennis ball hits the ground, we only need to worry about what happens up to that point. We can ignore the rebound for this part. Given:
d = -1.65
a = -9.8
vi = 0
vf = ?
*Keep in mind that the square root gives us two answers, a positve and a negative one. We use the negative one here because the final speed is downwards and the question says down is negative.
I think its when there are higher energies.