Answer:
v = 4.58 m/s
Explanation:
In order to calculate the speed of the skier when she gets the bottom of the hill, you have to calculate the speed of the skier when she crosses the rough patch.
To calculate the velocity at the final of the rough patch you take into account that the work done by the friction surface is equal to the change in the kinetic energy of the skier:
(1)
Where the minus sign means that the work is against the motion of the skier.
Wf: friction force
m: mass of the skier = 65.0kg
N: normal force = mg
g: gravitational acceleration = 9.8m/s^2
d: distance of the rough patch = 4.00m
v: speed at the end of the rough patch = ?
vo: initial speed of the skier = 6.85m/s
μk: coefficient of kinetic friction = 0.330
You replace the expression for the normal force in the equation (1), and solve for v:

Then, the speed fot he skier at the bottom of the hill is 4.58m/s
Near the Earth's surface, a freely falling body has constant acceleration at every instant of its fall ... 9.8 meters per second^2.
Rock is completely immersed in hot water. By the second law of thermodynamics, thermal energy or heat is transferred from substance with higher temperature to substance with lower temperature until they come to thermal equilibrium i.e. both at same temperature.
It is given here that rock is at 20°C which is at lower temperature than water at 80°C. ∴Heat or thermal energy flows from water to rock. So, right choice is-
A. The water gives the rock thermal energy and gets no thermal energy in return.
Answer:
A.−2.1 × 10^10 N
Explanation:
Using the formula;
E = k Q1Q2/d²
Where;
E is the electrical force
k is the constant
Q1, Q2 are the two charges and
d is the distance between the two charges
Therefore;
E = (9 x 10^9) × (0.0042) × (-0.0050) / (0.0030)²
= -2.1 x 10^10 N
Therefore; electrical force acting between the two charges is -2.1 x 10^10 N.