A running track measures 1056 ft per lap. To run 15.0 km, how many laps should you run?

46.6 laps

Explanation:

Step 1: Given data

Step 2: Convert "l" to km

We will use the conversion factor 1 km = 3280.84 ft.

1056 ft × (1 km / 3280.84 ft) = 0.3219 km

Step 3: Calculate the number of laps that you should run

We will use the following expression.

laps = d/l

laps = 15.0 km/(0.3219 km/lap)

laps = 46.6 laps

first one is the correct answer

first let us lay out the formula for potential

and kinetic energy:

pe = mgh

ke = (mv^2)/2

where: m=mass, v=velocity, g=gravitational

acceleration, h=height

calculating for mass using the known values of

pe:

340j = m (9.81 m/s^2) (50ft) (1m/3.28ft)

m = 2.27 kg

the law of conservation of energy states that

energy is neither created nor destroyed. therefore, the change in kinetic

energy from 50 ft to 35 ft would be equal to the change in potential energy

from 50 ft to 35 ft. however it would be opposite in signs since one is losing

while other is gaining.

ke(35ft) – ke(50ft) = - [ pe(35ft) – pe(50ft]

ke(50ft) = 0 since the brick is initially at rest

ke(35ft) = 340j - 2.27kg (9.81 m/s^2) (35ft)

(1m/3.28 ft)

ke(35ft)

= 102.38 j