Answer:
The car requires 192 feet to stop from a speed of 48 miles per hour on the same road
Step-by-step explanation:
- Direct proportion means that two quantities increase or decrease in the same ratio
- If y is directly proportional to x (y ∝ x) , then
<em>OR</em> y = k x, where k is the constant of proportionality
∵ The stopping distance d of an automobile is directly
proportional to the square of its speed s
- That means d ∝ s²
∴
∵ A car requires 75 feet to stop from a speed of 30 miles per hour
∴ d = 75 feet
∴ s = 30 miles/hour
- Change the mile to feet
∵ 1 mile = 5280 feet
∴ 30 miles/hour = 30 × 5280 = 158400 feet/hour
∵ The car require to stop from a speed of 48 miles per hour
on the same road
- Change the mile to feet
∴ 48 miles/hour = 48 × 5280 = 253440 feet/hour
∵
- Substitute the values of by 75 feet,
by 158400 feet/hour
and by 253440 feet/hour
∴
∴
- By using cross multiplication
∴ 25 × = 75 × 64
- Divide both sides by 25
∴ = 192 feet
The car requires 192 feet to stop from a speed of 48 miles per hour on the same road