Question

1. Determine the potential energy of a 2kg rock at the top of a hill that is 20m high.

2. Determine the kinetic energy of a 2000 kg roller coaster car that is moving with a speed of 25 m/s.

3. A 80kg freezer is located in an office on the 59 floor of an office building 200 meters above the ground. What is the potential energy of the freezer?

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Answer 1

`1)\:392\:\text{J}\:(400\:\text{J with one significant figure)},\\2)\:625,000\:\text{J}\:(600,000\:\text{J with one significant figure)},\\3)\:156,800\:\text{J}\:(200,000\:\text{J with one significant figure)},`

Step-by-step explanation:

1. The potential energy of an object is given by
`PE=mgh`. Substituting given values, we have:

`PE=2\cdot 9.8\cdot 20=\boxed{392\:\text{J}}`

2. The kinetic energy of an object is given by
`KE=(1)/(2)mv^2`. Substituting given values, we have:

`KE=(1)/(2)\cdot 2000\cdot 25^2 =\boxed{625,000\: \text{J}}`

3. 1. The potential energy of an object is given by
`PE=mgh`. Substituting given values, we have:

`PE=80\cdot 9.8\cdot 200=\boxed{156,800\:\text{J}}`

Answer 2

1) 392 joules

2) 625,000 joules

3) 156,800 joules

Step-by-step explanation:

Gravitational potential energy = mgh. m = mass in kg, g = acceleration due to gravity and h = height in meters.

Kinetic energy = 1/2(m)(v)^2, m = mass in kg, v = velocity in meters per second

1) P.E = 2 x 9.8 x 20 = 392 joules

2) K.E = 1/2 x 2000 x (25)^2 = 625,000 joules

3) P.E = 80 x 9.8 x 200 = 156,800 joules