Work needed = 23,520 J
<h3>Further explanation</h3>
Given
height = 12 m
mass = 200 kg
Required
work needed by the crane
Solution
Work is the transfer of energy caused by the force acting on a moving object
Work is the product of force with the displacement of objects.
Can be formulated
W = F x d
W = Work, J, Nm
F = Force, N
d = distance, m
F = m x g
Input the value :
W = mgd
W = 200 kg x 9.8 m/s²x12 m
W = 23520 J
Answer:
A) Increases by a factor of 2
Explanation:
Kinetic energy can be defined as an energy possessed by an object or body due to its motion.
Mathematically, kinetic energy is given by the formula;
Where;
K.E represents kinetic energy measured in Joules.
M represents mass measured in kilograms.
V represents velocity measured in metres per seconds square.
Given that mass, m = 2m
Substituting into the equation, we have;
K.E = ½mv²
K.E = ½*2mv²
Cross-multiplying, we have;
2K.E = 2mv²
Hence, if the mass of an object increases by a factor 2, kinetic energy is increased by a factor of 2.
1. Answer: A skydiver whose air resistance is equal to that of her weight.
A skydiver free falls under gravity but her rate of fall slows down due to drag -air resistance. when this air resistance becomes equal to her weight, the two get balanced and the body does not accelerate or decelerates.
2. Answer: Gravity
Contact forces are those which act when there is physical contact between two bodies. For example: normal force, tension and spring force.
Non-contact forces act between two bodies even when they are at a distance apart. For example: gravity, electric force, magnetic force etc.
3. Answer: The tendency of an object's motion to remain the same.
Inertia is a property of matter by virtue of which it tends to remain in its state of motion or rest. It does depend on mass of the object, more the mass, more is inertia. For example, cycle can be easily moved but we need real push hard for a car to move.
4. Answer: 254 N
The man pushes the box with 310 N force at an angle of 55 degrees to the horizontal.
we can write this in terms of horizontal ()and vertical component ().
Horizontal component:
Vertical component:
The vertical component would act towards the floor making the job more difficult to move the job.
Answer:
red shift, indicating that the universe is expanding
Explanation:
Doppler effect occurs when a source of a wave (e.g. light, or sound waves) moves relative to an observer; as a result of this relative motion, the wavelength of the wave appears lengthened/shortened to the observer. Two situations can occur:
- The source of the wave is moving towards the observer - in this case, the wavelength of the wave becomes shorter. If the wave is visible light, such as the light emitted by distant galaxies, this means that the wavelength of the light shifts towards the blue-end of the spectrum (blue-shift)
- The source of the wave is moving away from the observer - in this case, the wavelength of the wave becomes longer. If the wave is visible light, such as the light emitted by distant galaxies, this means that the wavelength of the light shifts towards the red-end of the spectrum (red-shift)
In our universe, we observe a red-shift for all the distant galaxies: this means that these galaxies are moving away from us, so this is an indication that the universe is expanding.