High School

A force of 3000 dynes acts on a mass of 300 grams for 10 seconds. Calculate the kinetic energy of the body after 10 seconds.

Answer :

The kinetic energy of the body after 10 seconds is 0.15 joules. This is calculated using the mass of the body, the force applied, and the time over which the force is applied to determine the final velocity and thus the kinetic energy.

To calculate the kinetic energy of a body after a force has been acting on it for a certain period, we need to determine the body's acceleration and then its final velocity after that period. The formula for kinetic energy (KE) is rac{1}{2}mv^2

First, let's convert the mass from grams to kilograms by dividing by 1000, so the mass m = 0.300 kg. Next, we'll use Newton's second law to find acceleration (F = ma), remembering to convert the force from dyne to newtons (1 N = 10^5 dynes). The force F = 3000 dynes is equivalent to F = 0.03 N. Now we can calculate the acceleration a = F/m = 0.03 N / 0.300 kg = 0.1 m/s^2.

Acceleration is constant, so the velocity after 10 seconds, v = at = 0.1 m/s^2 * 10 s = 1 m/s.

Hence, the kinetic energy KE = rac{1}{2} * 0.300 kg * (1 m/s)^2 = 0.15 J (joules).

Therefore, the kinetic energy of the body after 10 seconds is 0.15 joules.