Question

1. why is this expression for kinetic energy incorrect?

ke = (m)(v)².
a. the constant g is missing.
b. the term v should not be squared.
c. the expression should be divided by 2.
d. the energy lost to friction has not been subtracted.

1. what is the kinetic energy of a 10kg object moving at

2.0 m/s?
a. 10 j
b. 20 j
c. 40 j
d. 100 j

Explanation:

Question 26

Step1: Recall KE formula

The correct formula for kinetic energy is \( KE = \frac{1}{2}mv^2 \).

Step2: Analyze the given expression

The given expression is \( KE=(m)(v)^2 \). Comparing to the correct formula, it lacks the factor of \( \frac{1}{2} \).

Step3: Evaluate options

• Option a: \( g \) is for gravitational potential energy (or weight), not KE. Eliminate.
• Option b: \( v \) should be squared in KE. Eliminate.
• Option c: The expression needs to be divided by 2 (add the \( \frac{1}{2} \) factor). Correct.
• Option d: KE formula doesn't account for friction loss (that's for real - world energy changes, not the basic formula). Eliminate.

Step1: Recall KE formula

The formula for kinetic energy is \( KE=\frac{1}{2}mv^{2} \), where \( m = 10\space kg \) and \( v = 2.0\space m/s \).

Step2: Substitute values

Substitute \( m = 10 \) and \( v = 2.0 \) into the formula:
\( KE=\frac{1}{2}\times10\times(2.0)^{2} \)

Step3: Calculate step - by - step

First, calculate \( (2.0)^{2}=4.0 \). Then, \( \frac{1}{2}\times10 = 5 \). Finally, \( 5\times4.0 = 20\space J \).

Answer:

c. The expression should be divided by 2.

Question 27