Answer:

Explanation:
From the question we are told that:
Crane Length 
Crane Mass 
Arm extension at lifting end 
Arm extension at counter weight end 
Load 
Generally the equation for Torque Balance is mathematically given by



<span>The velocity would be 54.2 m/s
We would use the equation 1/2mv^2top+mghtop = 1/2mv^2bottom+mghbottom where m is the mass of the bobsled(which can be ignored), vtop/bottom is the velocity of the bobsled at the top or bottom, g is gravity, and htop/bottom is the height of the bobsled at the top or bottom of the hill. Since the velocity of the bobsled at the top of the hill and height at the bottom of the hill are zero, 1/2mv^2top and mghbottom will equal zero. The equation will be mghtop=1/2mv^2bottom. Thus we would solve for v.</span>
B. the ideas about the orbits of planets
A & B
Observe the path of the light ray as it passes through the lenses as shown in the attached images. Concave lenses diverge light rays while the convex lens converges the light rays.
Explanation:
Real images are formed where the rays converge, a property of images by convex lenses. Convex lenses can be used to magnify objects. If the image occurs before the focal point of the lens then the image will be upright but smaller. The images inverts and gets bigger past the focal point.
Virtual images are property of concave lenses. These images appear closer but smaller than the real object.
Learn More:
For more on images formed by lenses check out;
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Answer:
if the intensity of photons is constant then number of ejected electrons will remain same
Explanation:
As per photoelectric effect we know that when light of sufficient frequency fall on the surface of metal then electrons get ejected out of the surface with certain kinetic energy
Here the energy of photons is used to eject out the electrons from metal surface and to give the kinetic energy to the ejected electrons
so we have

here W = work function of metal which shows the energy required to eject out electrons from metal surface
KE = kinetic energy of ejected electrons
now if we increase the frequency of the photons that incident on the metal surface then in that case the incident energy will increase
So the electrons will eject out with more kinetic energy while if the number of photon is constant or the intensity of photons is constant then number of ejected electrons will remain same