Answer:
a. negative
b. zero
Explanation:
work is the change in the energy of a system due to external forces
work is done when a force moves a load through a distance in the direction of the force
The work done by a force on a system is positive when the force and the force displacement point in the same direction and negative when they point in opposite directions
in the scenario we are considering in the question, the force (the hand) moves the block vertically upwards but the displacement of the block reduces (in the opposite direction) since it decelerates. as such the work done by gravity on the block is negative.
the work done on the block is zero if the system consists of the block and the earth because there is no gravitational force exerted on the system
Answer:
= 17º C
Explanation:
This is a calorimetry problem, where heat is yielded by liquid water, this heat is used first to melt all ice, let's look for the necessary heat (Q1)
Let's reduce the magnitudes to the SI system
Ice m = 80.0 g (1 kg / 1000 g) = 0.080 kg
L = 3.33 105 J / kg
Water M = 860 g = 0.860 kg
= 4186 J / kg ºC
Q₁ = m L
Q₁ = 0.080 3.33 10⁵
Q₁ = 2,664 10⁴ J
Now let's see what this liquid water temperature is when this heat is released
Q = M ΔT = M (T₀₁ -)
Q₁ = Q
= T₀₁ - Q / M ce
= 26.0 - 2,664 10⁴ / (0.860 4186)
= 26.0 - 7.40
= 18.6 ° C
The initial temperature of water that has just melted is T₀₂ = 0ª
The initial temperature of the liquid water is T₀₁= 18.6
m + M = M T₀₁ - m T₀₂o2
= (M To1 - m To2) / (m + M)
= (0.860 18.6 - 0.080 0) / (0.080 + 0.860)
= 17º C
gg
two electrons are created from a quanta of kight
Answer: 4.17 m
Explanation: According to the law of conservation of energy, the elastic potential energy of the elastic material is used in launching the mass hence giving the body it potential energy.
Elastic potential energy = kx²/2
Potential energy = mgh
Where m = mass of object = 0.24kg
g = acceleration due to gravity = 9.8 m/s²
h = height =?
k = spring constant = 850 N/m
x = compression = 31cm = 0.13m
kx²/2 = mgh
kx² = 2× mgh
850 ×(0.31)² = 2 × 9.8 × h
h = 850 × (0.31)²/ 2 × 9.8
h = 81.685 / 19.6
h = 4.17 m