Answer:a
Explanation:
We have to lift the load two loads up one story, so energy required is
let m be the mass of each load and h is the height of each story
Energy 
Here energy gained is the potential energy which depends upon the datum(floor).
For lifting one load up one story
Energy required
thus 
is half of 
So option a is correct
Answer:
Explanation:
The bead is moving on a vertical circular path so it must have a centripetal force towards the centre.
This force is equal to m v² / r
v is velocity of bead and r is radius of the circular path.
The vertical hoop is also rotating about a vertical axis passing through the centre at frequency f so the bead will experience a cetrifugal force due to rotation of the hoop. Its value is
m ω² r . Only at the point o degree and 180 degree , these forces are opposite to each other so at these points , the bead will be in equilibrium .
mv² / r = m ω² r
v² = ω² r²
v = ω r
= 2π f r
= 2 x 3.14 x 2 x 0.22
v = 2.76 m /s
For the bead to rise upto point θ = 90 degree , height achieved is radius R
required velocity = √ 2gR
= √ 2x 9.8x.22
= 2.076 m/s
This velocity is less than the velocity calculated earlier so the bead will be able to ride the required height.
v = 2.76 m/s
Let the mass of 2500 kg car be 
and it's velocity be 
and the mass of 1500 kg car be 
and it's velocity be 
.
After the bumping the mass be M and it's velocity be V.
By law of conservation of momentum we have
2500 * 5 + 1500 * 1=4000 * V
V = 14000/4000 = 7/2 = 3.5 m/s
So the velocity of the two-car train = 3.5 m/s
<span>(20 cm)/(5 sec) = (0.20 meters)/(5 seconds)
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