Physics multiple choice help

[rz123]

my MMC reader not workin so can't upload image. i will get to know the answer thanks anyways.

 

[rz123]

A ball is fired upwards with an initial velocity of 30m/s.table below shows how the ball's velocity changes. g=9.81
a) complete the table
draw a graph of the data nd use it to deduce how long the ball took to reach its highest point.

velocity: 30 ,20.19 , __ , __ , __ , __

time : 0 , 1 , 2 , 3 , 4 , 5

 

[destined007]

A ball is fired upwards with an initial velocity of 30m/s.table below shows how the ball's velocity changes. g=9.81
a) complete the table
draw a graph of the data nd use it to deduce how long the ball took to reach its highest point.

velocity: 30 ,20.19 , __ , __ , __ , __

time : 0 , 1 , 2 , 3 , 4 , 5

 

[rz123]

why did we used v= u-gt , g is taken negative all the way thru journey? it shud be - or + one way while going up or when it starts to fall down after reaching max height.

 

[rz123]

q. a stone is thrown with a velocity of 8m/s into the air at an angle of 40 degree to the horizontal
a) calculate the vertical component of the velocity
b) state the value of the vertical component of the velocity when the stone reaches its highest point. ignore air resistance
c) use ur answers to A nd B to calculate the time the stone takes to reach its highest point.
d) calculate the horizontal component of the velocity
e) use ur answers to c nd d to find the horizontal distance traveled by the stone while climbing to it highest point.

DON'T SOLVE WHOLE, PROBLEM IN PART C AND E ONLY!

 

[destined007]

why did we used v= u-gt , g is taken negative all the way thru journey? it shud be - or + one way while going up or when it starts to fall down after reaching max height.

When an object is thrown up initially, its g is -ve. It doesn't matter if it comes down after reaching its maximum height.

 

[rz123]

par yar jab neche a raha hay object toh phr toh + nai ho jay as it is in the direction of gravity. chalo choro. nd thanks a lot yar . kis nikamay se pala parh gya tmhara haha. yelo phr aik aur question :|

 

[rz123]

the velocity time graph represents the motion of car along a straight road for a period of 30 s.
displacement calculated by area under graph was 420 m,
next part says: check your answer to part d by calculating the car's displacement using s=ut+1/2at^2
my question is in order to check by this formula why did we used U to be 8m/s rather then 20 m/s as this is the initial velocity.

 

[destined007]

Here:

 

[rvelzahid]

help required bro.

 

[destined007]

 

[rvelzahid]

help Sir destined 007! :Search:

 

[destined007]

F=rate of change of momentum with respect to time
F=(m1v1-m1v2)/T
F=m1(v1-v2)/T

rate of change of mass is given as m1/T=10kgs^-1 (note that time is already included in this mass because its a rate)
the initial velocity is v1= 5 ms^-1
there is no final velocity because the water didn't rebound, so v2=0

F=10(5-0) =50 N

 

[rockheart123]

can u help me with two questions..one from oct/2007 ques 23 and one from may/2008 ques 24...

 

[destined007]

Q23) V=fλ
f=8/50=0.16 Hz

max v=2 π fa=2 π 0.16 (2)
v=0.64 π

KE=1/2mv^2
KE=1/2 2.0 × 10–3 (0.64 π )^2
=4 mJ


Q24) Young modulus will be the same because the material is same

 

[rz123]

answers :a) 50 GPa , b) 100GPa, c) 25GPa
how to calculate young modulus of the graphs in the pic (formula not working), and can we calculate stress over any part of the straight line in each graph or the value for stress should be the elastic limit point ?

Thanks a lot.

 

[destined007]

Calculate young modulus for the point when materials are following hooks law.
young modulus: stress/strain

for a)
stress=100 x 10^6 Pa
strain=0.2 %= 0.2/100=2x10^-3
YM=(100x10^6)/(2x10^-3)=50x10^9=50 GPa

now do for other two.

 

[rz123]

hi , A car battery is labelled 50Ah. his means that it can supply a current of 50A for one hour.
a) for how long could the battery supply a continuous current of 200 A needed to start the car?
Ans:15 minutes

 

[rz123]

hi , A car battery is labelled 50Ah. his means that it can supply a current of 50A for one hour.
a) for how long could the battery supply a continuous current of 200 A needed to start the car?
Ans:15 minutes

 

[destined007]

Q=It
Q=50 x 3600
Q=180000 C

Q=It
180000=200 x t
t=900 s = 15 min