Question

q.10. there is a box at the top of a hill that is 10 m high and the box has a mass of 20 kg. what is the potential energy of the box? (g = 9.8 m/s²) a) 200 joules b) 2000 joules c) 98 joules d) 1960 joules q.11. there is a 10 kg box at the top of a tower that is storing 490 joules of energy. what is the height of the tower? (g = 9.8 m/s²) a) 5 m b) 10 m c) 50 m d) 100 m q.12. the potential energy of a box is 1960 joules. the box is 20 m high. what is the mass of the box? (g = 9.8 m/s²) a) 2 kg b) 5 kg c) 10 kg d) 50 kg q.13. a 6 kg dog has 300 joules of kinetic energy. how fast is it moving? a) 5 m/s b) 10 m/s c) 20 m/s d) 50 m/s

Explanation:

Q.10

Step1: Recall potential - energy formula

The formula for gravitational potential energy is $U = mgh$, where $m$ is mass, $g$ is acceleration due to gravity, and $h$ is height.
Given $m = 20\ kg$, $g=9.8\ m/s^{2}$, and $h = 10\ m$.

Step2: Substitute values

$U=20\times9.8\times10=1960\ J$

Step1: Rearrange potential - energy formula for height

From $U = mgh$, we can solve for $h$ as $h=\frac{U}{mg}$. Given $U = 490\ J$, $m = 10\ kg$, and $g = 9.8\ m/s^{2}$.

Step2: Substitute values

$h=\frac{490}{10\times9.8}=5\ m$

Step1: Rearrange potential - energy formula for mass

From $U = mgh$, we can solve for $m$ as $m=\frac{U}{gh}$. Given $U = 1960\ J$, $h = 20\ m$, and $g = 9.8\ m/s^{2}$.

Step2: Substitute values

$m=\frac{1960}{9.8\times20}=10\ kg$

Answer:

d) 1960 joules

Q.11