Question

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

Answer 1

Answer:

1) 392 joules

2) 625,000 joules

3) 156,800 joules

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

Answer 2

Answer:

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

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 $KE=\frac{1}{2}mv^2$. Substituting given values, we have:

$KE=\frac{1}{2}\cdot 2000\cdot 25^2 =\boxed{625,000\: \text{J}}$

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

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