Question

1. a toy car is moving along with 0.40 joules of kinetic energy. if its speed is doubled, then its new kinetic will be ______.

a) 0.10 j
b) 0.20 j
c) 0.80 j
d) 1.60 j
e) still 0.40 j

Explanation:

Step1: Recall Kinetic Energy Formula

The formula for kinetic energy is \( KE = \frac{1}{2}mv^2 \), where \( m \) is mass and \( v \) is speed.

Step2: Analyze Initial and New Kinetic Energy

Let the initial speed be \( v \) and mass be \( m \), so initial \( KE_1=\frac{1}{2}mv^2 = 0.40\space J \).
When speed is doubled, new speed \( v_2 = 2v \). New kinetic energy \( KE_2=\frac{1}{2}m(2v)^2 \).

Step3: Simplify New Kinetic Energy

Simplify \( KE_2=\frac{1}{2}m\times4v^2 = 4\times(\frac{1}{2}mv^2) \).
Since \( \frac{1}{2}mv^2 = KE_1 = 0.40\space J \), substitute: \( KE_2 = 4\times0.40 = 1.60\space J \).

Answer:

d) 1.60 J