An object moving with a speed of 21m/s and has a kinetic energy of 140 J.what is the mass of the object.

The formula for kinetic energy is:<br /><br />\[<br />KE = \frac{1}{2} m v^2<br />\]<br /><br />Where:<br />- \( KE \) is the kinetic energy,<br />- \( m \) is the mass of the object,<br />- \( v \) is the velocity (speed).<br /><br />Rearranging the formula to solve for \( m \):<br /><br />\[<br />m = \frac{2 \cdot KE}{v^2}<br />\]<br /><br />Substitute the given values (\( KE = 140 \, \text{J} \), \( v = 21 \, \text{m/s} \)):<br /><br />\[<br />m = \frac{2 \cdot 140}{21^2}<br />\]<br /><br />First, calculate \( 21^2 \):<br /><br />\[<br />21^2 = 441<br />\]<br /><br />Now substitute back:<br /><br />\[<br />m = \frac{2 \cdot 140}{441} = \frac{280}{441}<br />\]<br /><br />Simplify:<br /><br />\[<br />m \approx 0.635 \, \text{kg}<br />\]<br /><br />Thus, the mass of the object is approximately **0.635 kg**.