The speed of a car after accelerating for 8 seconds is inversely proportional to its weight. The car weighs 1600 kg and accelerates to 100 km/h in 8 seconds. What is the speed after accelerating for 8 seconds if we load the car with 800 extra kg to 2400 kg?

With 800 extra kg load: speed = 66.667 km/h

With 2400 extra kg load: speed = 40 km/h

Step-by-step explanation:

Let's call the weight of the car W = 1600 kg, and its speed after accelerating for 8 seconds with this weight S = 100 km/h

If we load the car with 800 extra kg, the total weight will be:

W2 = W + 800 = 2400 kg

The relation between the weights is:

W2 / W = 2400 / 1600 = 1.5

If the weight increased 1.5 times, the relation between the speeds will be 1/1.5 (as they are inversely proportional), so:

S2 / S = 1 / 1.5

S2 = S / 1.5 = 66.667 km/h

If we load the car with 2400 extra kg, the total weight will be:

W3 = W + 2400 = 4000 kg

The relation between the weights is:

W3 / W = 4000 / 1600 = 2.5

If the weight increased 2.5 times, the relation between the speeds will be 1/2.5, so:

S3 / S = 1 / 2.5

S3 = S / 2.5 = 40 km/h