Question

a projectile of mass 50 gm is fired with velocity 10m s at an angle 30 with the horizontal calculate the linear momentumand kinetic energy of the projectile at highest point?

Answer 1

At the highest point the vertical component of the velocity will be zero, do you agree with this?

Answer 2

becoz it was fired horizantly

Answer 3

If it was given only vertical velocity, then also at the highest point it'd be zero

Answer 4

at the highest point linear momentum would be mucos theta

Answer 5

\[v ^{2}= u ^{2} - 2as\] u is 10 sin theta, a is acc due to gravity, find s, then we use it to find potential energy which is mgs which we get 125 so energy is 125

Answer 6

can we do lik this? k.e= 1/2 m sq(u cos theta)

Answer 7

sorry it is 6.25, @mathavraj i thought it is safe to just see change in height

Answer 8

@mathavraj i think we can. ucos theta is the velocity at the highest point. sub it in formula for KE should give us the answer.

Answer 9

i got KE as 1.87 J

Answer 10

@Ruchi what is the answer?

Answer 11

@Vaidehi09 what did u do?

Answer 12

KE = 1/2 m u^2 cos^2(30)

Answer 13

it should be sin thta na?

Answer 14

theta is the angle with the horizontal. so horizontal component of velocity will have cos..not sin

Answer 15

no u sin theta is zero at top

Answer 16

yes and ke energy is chaange in velocity so it will be 1/2m(vi-vf)

Answer 17

pls explain @rdx

Answer 18

well kinetic energy is change in its intial energy and final energy so taking sin theta or cos theta should not make a difernece ,

Answer 19

so let me do this by taking cos component in consideration \[1/2m(v \cos 30-v \cos 0)^{2}\]

Answer 20

check it wid sin shoot me if u get any other result :P

Answer 21

@mathavraj any problem??

Answer 22

its zero wen we use sin component..but i still dint get that change thing..at the highst point there is only cos component...wich is constant throught the motion

Answer 23

umm wait

Answer 24

sorry i made a mistake again but 6.25 is correct. u urself agree that that there is no change in cos componet so there is no change in kinetic energy in x direction but only change in kinetic energy y direction and initially K.E in y direction is 6.25 and finally it is 0 so initial - fianl is the net K.E

Answer 25

so should we take sin also

Answer 26

what do u wnat to say?

Answer 27

@Ruchi. what is the answer?

Answer 28

i don't know its answer is nt mention

Answer 29

we don;t hav to use its mass

Answer 30

?

Answer 31

y not mass?

Answer 32

1/2"M"v^2

Answer 33

@Rdx ?

Answer 34

yes what do u want? u will need mass to find the energy, whenever a qustion asks potential or kinetic energy u actually need to calculate change in potential or kinetic energy

Answer 35

best is solve by seeing change in height

Answer 36

@Rdx KE at the highest point = KE in x direction + KE in y direction.....right?
but velocity in y direc at that pt = 0
so KE at highest pt = KE in x direc........or am i wrong?

Answer 37

IT IS CHANGE IN KINETIC ENERGY,

Answer 38

well the x componet of velocity remains constant throughot and the change is y componet