Question

a bullet of mass 20 grams initially moving horizontally with velocity 150 m/s penetrates 20 cm into a fixed wooden block if the magnitude of an average resistance force exerted by the wooden block is K * 225 N. the value of K is

Answer 1

Resistance offered- F=ma ,where m=20g=.02kg acclⁿis to be determined. v²=u²+as as bullet isstoppedafter 20 cm in plank v=0 ,u=150m/s ,s=20cm=0.2m On substituting 0²=150²+2a*0.2 a=-22500/0.4 a=-56250(- sign represents deceleration) F=0.02*56250 (only magnitude of acclⁿas we are not told to find F vector) F=1125N=Resistance offered by wooden plank 1125=Kx225 then K=5