Answer:
Explanation:
Q = m c Δt
heat withdrawn to lower temperature by 40° C
Q = 1 X 1000 X 40 = 40,000 calories.
Q = mL
heat withdrawn to freeze water at 0°C to ice
= 1 x 80000 = 80,000 calories
total heat to be withdrawn = 120,000 calories. = 120,000 x 4.2 = 504 ,000 Joules.
Answer: a magnetic field is created by moving electric charges
Answer:
a) E = 2.00 10³ J
, b) I = 6.66 10⁻⁶ N s
, c) F = 1.66 10⁻⁶ N
Explanation:
a) The intensity is defined as the power per unit area
I = P / A
P = I A
Power is energy for time
P = E / t
We replace
E / t = I A
E = I A t
E = 1.0 10³ 2.0 1.00
E = 2.00 10³ J
b) The moment is
p = U / c
In the case of a reflection the speed is reversed, so the moment
Δp = 2 U / c
I = Δp
I = 2 U / c
I = 2.00 10³/3 10⁸
I = 6.66 10⁻⁶ N s
c) The defined impulse is
I = F t
F = I / t
For a time of 1 s
F = 6.66 10⁻⁶ / 1
F = 1.66 10⁻⁶ N
d) Suppose n small mass mirror m = 10 10⁻³ kg, we write Newton's second law
F = ma
a = F / m
a = 1.66 10⁻⁶ / 10 10⁻³
a = 1.66 10⁻⁴ m / s
We see that the acceleration is very small and attended to increase the mass of the mirror will be less and less, so the assumption of no twisting of the mirror is very reasonable
Commensalism: only one species benefits while the other is neither helped nor
harmed
so the relationship is Commensalism
Answer:
(a) 0
(b) 10ML
(c) 
(d) 
Explanation:
(a) When hanging straight down. The child is at the lowest position. His potential energy with respect to this point would also be 0.
(b) Since the rope has length L m. When the rope is horizontal, he is at L (m) high with respect to the lowest swinging position. His potential energy with respect to this point should be
where g = 10m/s2 is the gravitational acceleration.
(c) At angle 
from the vertical. Vertically speaking, the child should be at a distance of 
to the swinging point, and a vertical distance of 
to the lowest position. His potential energy to this point would be:
(d) at angle 
from the horizontal. Suppose he is higher than the horizontal line. This would mean he's at a vertical distance of 
from the swinging point and higher than it. Therefore his vertical distance to the lowest point is 
His potential energy to his point would be:
