Answer: 375
Step-by-step explanation:
Since we are given the information that there are 250 bricks used to build a wall 20 feet high, the number of brick used per feet will be:
= 250/20
= 12.5 bricks per feet.
Therefore, the number of bricks that will be used to buld a wall that is 30 fet high will be:
= 12.5 × 30
= 375 bricks.
Therefore, 375 bricks would be used.
Given Information:
Area of rectangle = 16 square feet
Required Information:
Least amount of material = ?
Answer:
x = 4 ft and y = 4 ft
Step-by-step explanation:
We know that a rectangle has area = xy and perimeter = 2x + 2y
We want to use least amount of material to design the sandbox which means we want to minimize the perimeter which can be done by taking the derivative of perimeter and then setting it equal to 0.
So we have
xy = 16
y = 16/x
p = 2x + 2y
put the value of y into the equation of perimeter
p = 2x + 2(16/x)
p = 2x + 32/x
Take derivative with respect to x
d/dt (2x + 32/x)
2 - 32/x²
set the derivative equal to zero to minimize the perimeter
2 - 32/x² = 0
32/x² = 2
x² = 32/2
x² = 16
x =
ft
put the value of x into equation xy = 16
(4)y = 16
y = 16/4
y = 4 ft
So the dimensions are x = 4 ft and y = 4 ft in order to use least amount of material.
Verification:
xy = 16
4*4 = 16
16 = 16 (satisfied)
160/55.
Simplified version is 32/11
Answer:
108,000 joules
Step-by-step explanation:
Kinetic energy, k = 1/2 mv^2
Where,
m = mass of the object in kilogram
v = velocity in meters per seconds
If
Velocity of an object = 20 meters per seconds
Kinetic energy = 48,000 joules
Solve for m
k = 1/2 mv^2
48,000 = 1/2 × m × 20^2
48,000 = 1/2 × m × 400
48,000 = 200m
m = 48,000 / 200
m = 240 kg
If it speeds up to 30 meters per second, then what is its new kinetic energy?
k = 1/2 mv^2
Using m = 240 kg
k = 1/2 mv^2
= 1/2 × 240 × 30^2
= 1/2 × 240 × 900
= 216,000 / 2
= 108,000 joules
The new kinetic energy = 108,000 joules