Create your Smart Home App in the Free Webinar on Home Automation. Register Now
One of our academic counsellors will contact you within 1 working day.
Click to Chat
1800-1023-196
+91-120-4616500
CART 0
Use Coupon: CART20 and get 20% off on all online Study Material
Welcome User
OR
LOGIN
Complete Your Registration (Step 2 of 2 )
Free webinar on App Development Learn to create your own Smart Home App
16th Jan @ 5:00PM for Grade 1 to 10
Sit and relax as our customer representative will contact you within 1 business day
An open knife of mass m is dropped from a height h on a wooden floor. if the blade penetrates up to the depth d into the wood,average resistance offered by the wood to the knife is?????
knife is dropped from A with u= 0 m/s FROM A----->B when it strikes the ground at B its velocity is: v2 - u2 = 2as v2- 0 = 2 (g) (h) v= √2gh----------------------------------------(1) after striking the ground it travels a distance ''d'' in this case u= √2gh {from (1)} v=0 s= d therefore, v2- u2= 2as 0 - 2gh= 2(a)(d) -2gh/2d=a a= -gh/d Now, force applied by the ground is = ma= m(-gh/d) = -mgh/d.
knife is dropped from A with u= 0 m/s
FROM A----->B
when it strikes the ground at B its velocity is:
v2 - u2 = 2as
v2- 0 = 2 (g) (h)
v= √2gh----------------------------------------(1)
after striking the ground it travels a distance ''d''
in this case u= √2gh {from (1)}
v=0
s= d
therefore, v2- u2= 2as
0 - 2gh= 2(a)(d)
-2gh/2d=a
a= -gh/d
Now, force applied by the ground is = ma= m(-gh/d) = -mgh/d.
On conserving mechanical energy we get velocity before penetration i.e{½mu²+mgh=½mv²}we got (v=√2gh)Now u=√2ghV=0Distance=s travelled by blade during its penetration.using eqñ (2as=v²-u²)we get acceleration to be (gh/s).now drawing it free body diagram we get an eqñ(mg-N=ma)putting value of a i.e acceleration we N=mg[1+h/s].where N is normal reaction or resistive force by the wooden surface during its penetration.
The initial KE + final kinetic energy+ (+ve) WD +(-ve) WD will be equal to final Work done.....KE1+(W+)+(W-)=KEf0+mg(h+d)-Fr(d)=0mg(h+d)=Fr(d)Fr=mg(1+h/d)
Post Question
Dear , Preparing for entrance exams? Register yourself for the free demo class from askiitians.
points won -