Question

The speed(S) of a car varies partly directly as its mass(M) and partly directly as the quantity (Q) of fuel in it. When the speed is 80km/hr, the mass is 220kg and the quantity of fuel is 30litres, when the speed is 60km/hr, the mass is 300kg and the quantity of fuel is 40 litres. Find the volume of fuel if the speed is 100km/hr and the mass 250kg. DO NOT WRITE TRASH I WILL REPORT YOU

Answer 1

Answer:

Quantity of fuel is 24 L, based on the model S=2400/Q when S=100

Step-by-step explanation:

If the output power of the car remains constant, the speed would reduce as the masses increase, which is the shown in the observed data.

Hence S does NOT vary directly with the mass and quantity, but varies INVERSELY with the mass and fuel (which has a mass).

Many models are possible to fit the results.  Product models with a single constant k

S(m,q) = kmq  and S(m,q) = k/mq  

do not fit both observation, hence rejected.

A possible  model with two constants is shown below

S(m,q) = k1/m + k2/q..................(1)

1.  m=220, q=30 =>  80 = k1/220 + k2/30 ..........(2)

2. m=300, q=40 =>  60 = k1/300 + k2/40 ..........(3)

Solve system (2) and (3) gives k1=0, k2 = 2400.

So it appears that the speed is independent of the mass (m) [unlikely], but inversely proportional to the quantity (q) of fuel, giving

S(q) = 2400/q

When speed = 100 km/h, and mass = 250 kg,  substitute

100 = 2400/q => q=2400/100 = 24