Question

In a shooting competition, a contestant fires a bullet of mass 100 g with speed of 400 m/s on a soft plywood of thickness 5 cm. The bullet emerges with 4% of its initial kinetic energy. Then emergent speed of the bullet is 160 m/s 16 m/s s /s s s 80 m/s 240 m/s​

Answer 1

Answer:

80m/s

Explanation:

kinetic energy =1/2mv² has been used

Answer 2

Given is the speed and mass of a bullet, find its emergent speed from the ply.

Explanation:

• The kinetic energy of a body having mass 'm' and moving with speed 'v' is given by, $K.E=\frac{1}{2} mv^2$
• Hence initially when the bullet is fired we have, $m=100\ g=0.1\ kg\ \ \ \ \ \ \ v_i=400\ m/s$  
• Therefore the initial kinetic energy of the bullet is, $KE_i=\frac{1}{2}mv_i^2$  
• Since it's given that the kinetic energy of the bullet after emerging from the wooden ply $4\%$ is that of initial.
• Let the emergent speed of the bullet be $v_e$ then we have,
• $KE_e=\frac{4}{100} KE_i\\->\frac{1}{2}mv_e^2= \frac{4}{100} (\frac{1}{2}mv_i^2)\\->v_e^2=\frac{4v_i^2}{100} \\->v_e=\frac{v_i}{5}\\->v_e=\frac{400}{5} \\->v_e=80\ m/s$  
• The emergent speed of the bullet is $80\ m/s$.