X + y = 5
x = 5 - y
2x - y = 7
2(5-y) - y = 7
10 - 2y - y = 7
10 - 3y = 7
10 - 7 = 3y
3 = 3y
y = 1
x + y = 5
x + 1 = 5
x = 5 - 1
x = 4
Conduction: someone burning their hand by placing their hand on a hot stove.
Convection: Food cooking in an oven.
Radiation: The heat we feel from the sun.
Answer:
Archaeologist use radioactive isotopes to determine the ages of various objects, rocks and materials. This is called radioactive dating. Radioactive isotope Carbon-14 is widely used for this dating process.
Scientists use radioactive isotopes in agriculture to monitor or study the uptake and use of essential nutrients by plants from the soil. This helps to determine viability, productivity and nutritious ability of the plants on a piece of land.
Geologists use radioactive isotopes to trace leaks in underground water storage, pipes. Radioactive isotopes are effective tracers because their radioactivity can be easily detected.
Answer:
Q = 59565 [J]
Explanation:
In order to calculate the amount of thermal energy needed we must use the following equation.

where:
m = mass = 150 [g]
Cp = 4.18 [J/g*°C]
Tfinal = 5 [°C]
Tinitial = 100 [°C]
Now replacing:
![Q=150*4.18*(100-5)\\Q=59565[J]](https://tex.z-dn.net/?f=Q%3D150%2A4.18%2A%28100-5%29%5C%5CQ%3D59565%5BJ%5D)
Answer:
(A) The maximum height of the ball is 40.57 m
(B) Time spent by the ball on air is 5.76 s
(C) at 33.23 m the speed will be 12 m/s
Explanation:
Given;
initial velocity of the ball, u = 28.2 m/s
(A) The maximum height
At maximum height, the final velocity, v = 0
v² = u² -2gh
u² = 2gh

(B) Time spent by the ball on air
Time of flight = Time to reach maximum height + time to hit ground.
Time to reach maximum height = time to hit ground.
Time to reach maximum height is given by;
v = u - gt
u = gt

Time of flight, T = 2t

(C) the position of the ball at 12 m/s
As the ball moves upwards, the speed drops, then the height of the ball when the speed drops to 12m/s will be calculated by applying the equation below.
v² = u² - 2gh
12² = 28.2² - 2(9.8)h
12² - 28.2² = - 2(9.8)h
-651.24 = -19.6h
h = 651.24 / 19.6
h = 33.23 m
Thus, at 33.23 m the speed will be 12 m/s