Question

1- A student lifts a 50 pound (lb) ball 4 feet (ft) in 5 seconds (s). How many joules of work has the student completed? 2- what is the kinetic energy of a jogger with a mass of 65 kg traveling with a speed of 2.5 m/s? 3- find the potential energy of a street light that has mass of 13 kg and is 4.8 meters above the ground. 4. What distance is a book from the floor if the book contains 196 joules of potential energy and has a mass of 5 kilograms?

Answer 1

Answer:

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Answer 2

Final answer:

1. 272.4joule work is completed by the student
2. The kinetic energy of a jogger is 81.25joule.
3. The potential energy of a street light is 624joule.
4. The distance of the book from the floor is 3.92m

Explanation:

1. Given that m = 50 pound

1 pound =  0.454kg

So, m = 50 × 0.454 = 22.7kg

h = 4feet

1 foot = 0.30m

So, h = 4 × 0.30 = 1.2m

Now, we know that

W = mgh

W = 22.7kg × 10m/s² × 1.2m

W = 272.4kgm²/s²

W = 272.4 joule.

2.  mass of the jogger, m = 65kg

                                     v = 2.5m/s

So, Kinetic energy

$K = \frac{1}{2}mv^2$

$K = \frac{1}{2}(65)(2.5)$

K = 81.25 joule.

3. m = 13kg

    h = 4.8m

Potential energy, U = mgh

U = 13 × 10 × 4.8 = 624 joule.

4. U = 196 joule

    m = 5kg

We know that,

U = mgh

$h = \frac{U}{mg}\\h = \frac{196}{(10)(5)}\\h = 3.92m$