A good question

A machine gun of mass M/4 is mounted on a plank of mass 3M/4. The barrel of the gun is inclined at an angle of θ with the horizontal. The plank is moving on a smooth horizontal surface in x-y plane of a coordinate system along positive y axis with a speed V. A bullet is fired with the speed u relative to the plank in x-z plane. Find the coordinates of the bullet with respect to the point of projection, which is fixed in the ground reference frame, at t=u/g (assuming the bullet does not fall back to the ground till this time). The positive Z axis is vertically upwards!

TAKE THE MASS OF THE BULLET TO BE m

16 Answers

11
virang1 Jhaveri ·

x = u2cosθ/g

z= u2(2sinθ - 1)/2g

is it rite?

6
Aakash Sharawat ·

no yaar this is not the answer!

there should be mass term too included!
this is not the answer!

3
nihit.desai ·

hey then the mass of bullet shud be given !! if we have to apply conservation of linear p, they shud give the mass of the fired bullet !!

3
nihit.desai ·

if we are simply to apply kinematics, then i think mass will not be involved newhr...

6
Aakash Sharawat ·

oh thats a blunder! i am sorry the mass of the bullet is m

6
Aakash Sharawat ·

no no you have to get the mass in the answer!

this is the complete question now i have rechecked! sorry could not continue th link i am leaving for gym!

1
skygirl ·

gym ???!~@!@$!!!!!!!!!! :O :O :O

good man!!

24
eureka123 ·

body shoddy bana raha hai kya???????[3][3]impress everyone in IIT[9][9]

1
skygirl ·

hhehehheheh [9]

1
MATRIX ·

wats gym???........

1
°ღ•๓яυΠ·

gym yaar jahan log excerzie karte hai

24
eureka123 ·

ohho prajith,,,,..u dont know what a gym is??????????[3][3]

6
Aakash Sharawat ·

no no eureka nothing like this! its all a part of daily routine! so i have to go for two hours, one hr in morning and one in evening! well the most important of all

KOI MUJHE ISKA SOLUTION DE DO!!!!!!!!!!!!!!

for the students who do not understand hindi,

RELP I NEED THE SOLUTION!!!!!!!!!!

1
Rohan Ghosh ·

well let the velocity of the combined system of machine gun and plank be v1 along negative x axis and v2 along y axis after the bullet is unleashed

then as the bullet was launched at a speed u w.r.t the gun the velocity of the bullet w.r.t the gun along y axis must be zero
(AS the gun is atr an uniform angle theta in x z plane
)

let the actual velocity of the gun be v3 with an angle of β to the x,z plane with x

Further as the bullet is launched perpendicular to the motion of the plank the relative velolcity along y must be zero

Mv=(M-m)v2+mvx

but vx=v2

thus we get v2=v and velocity of the bullet along y= v

further consercing momentum in the x-z plane

(M-m)v1=mv3cosβ

as the velocity of the bullet w.r.t plank is u ,its horizontal and vertical components must be ucos and usin theta

thuis

v3cosβ+v1=ucosθ
v3sinβ=usinθ

solving we get v3 cosβ and v3sinβ as the following

ucosθ-(mucosθ/M)
and usinθ

hence y coordinate=vt=vu/g
z coordinate= vsinβt-1/2gt2=u2/g(sinθ-1/2)
x coordinate=v3cosβt=u2cosθ/g(1-(m/M))

6
Aakash Sharawat ·

well the answer is:

6
Aakash Sharawat ·

rohan is got the correct answer!

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