Kinetic Energy Physics Example 2

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Example 2

medium
A car doubles its speed from 15 m/s15 \text{ m/s} to 30 m/s30 \text{ m/s}. By what factor does its kinetic energy change?

Solution

  1. 1
    Initial KE: KE1=12m(15)2=225m2KE_1 = \frac{1}{2}m(15)^2 = \frac{225m}{2}.
  2. 2
    Final KE: KE2=12m(30)2=900m2KE_2 = \frac{1}{2}m(30)^2 = \frac{900m}{2}.
  3. 3
    Ratio: KE2KE1=900225=4\frac{KE_2}{KE_1} = \frac{900}{225} = 4

Answer

KE increases by a factor of 4\text{KE increases by a factor of } 4
Because kinetic energy depends on velocity squared, doubling the speed quadruples the kinetic energy. This is why high-speed collisions are so much more dangerous.

About Kinetic Energy

The energy an object possesses by virtue of its motion, equal to one-half times its mass times the square of its velocity.

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Example 1 easy

What is the kinetic energy of a [formula] ball moving at [formula]?

Example 3 medium

A [formula] ball has [formula] of kinetic energy. What is its speed?

Example 4 easy

A [formula] car doubles its speed from [formula] to [formula]. By what factor does its kinetic energ

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