Question

What is the Kinetic Energy of a 155 kg object that is moving at a speed of 20 m/s?

a
3100 J
b
31,000 J
c
18,619 J
d
2,402,500 J

Answer 1

The formula for kinetic energy (KE) is given by:

\[
KE = \frac{1}{2}mv^2
\]

where:
- \( m \) is the mass of the object,
- \( v \) is the speed of the object.

Given:
- \( m = 155 \) kg
- \( v = 20 \) m/s

Now, let's plug in the values:

\[
KE = \frac{1}{2} \times 155 \, \text{kg} \times (20 \, \text{m/s})^2
\]

Calculating \( (20 \, \text{m/s})^2 \):

\[
(20)^2 = 400 \, \text{m}^2/\text{s}^2
\]

Now substituting back into the kinetic energy formula:

\[
KE = \frac{1}{2} \times 155 \, \text{kg} \times 400 \, \text{m}^2/\text{s}^2
\]
\[
KE = \frac{1}{2} \times 62000 \, \text{kg} \cdot \text{m}^2/\text{s}^2
\]
\[
KE = 31000 \, \text{J}
\]

So, the kinetic energy of the object is \( 31,000 \, \text{J} \).

The correct answer is **b) 31,000 J**.