1. Derive the formula for potential energy.
2. Explain the Law of conservation of energy with pendulum.
3. If energy is neither created nor destroyed then from where do we get energy?
4. State and explain one example where kinetic energy is present in a body and is used.
5. Define power and give its unit.
6. What is potential energy? Explain different types of potential energy.
7. How is work and energy related to each other?
8. Give one example where work done on an object is negative.
9. A man does 60 J of work in 6 seconds. Calculate the power.
10. Give one example where work done on an object is zero.
Share
Answer:
1.Potential energy is the energy stored in the body due to its position or its configuration. Some examples of potential energy include an object held at height, a compressed spring, a stretched rubber band, etc. Potential energy for any object is given by the formula, P.E. = mgh.
2.For example, when a pendulum swings upward, kinetic energy is converted to potential energy. When the pendulum stops briefly at the top of its swing, the kinetic energy is zero, and all the energy of the system is in potential energy.
3.The law of conservation of energy states that the total energy of an isolated system remains constant—it is said to be conserved over time. Energy can neither be created nor destroyed; rather, it transforms from one form to another. Hence the statement is correct.
4.Watermills are powered by the kinetic energy of running water. Moving air has kinetic energy, which is used to power windmills and propels sailing boats; similarly, a bullet fired from a cannon has kinetic energy, which allows it to penetrate a target.
5.We can define power as the rate of doing work, it is the work done in unit time. The SI unit of power is Watt (W) which is joules per second (J/s). Sometimes the power of motor vehicles and other machines is given in terms of Horsepower (hp), which is approximately equal to 745.7 watts.
6.Potential energy is energy that is stored in an object or substance. The two main types of potential energy are gravitational potential energy and elastic potential energy.
7.Work and energy are closely related. When you do work to move an object, you change the object's energy. You (or an object) also expend energy to do work. In fact, energy can be defined as the ability to do work.
8.When the applied force on an object and the displacement of the object are in opposite direction, the work done is knows as negative. A rocket is a good example of negative work.
9.. A man does 60 J of work in 6 seconds. Calculate the power.Solve ForKnown 1 Identify knowns & unknowns This question is asking to find power with knowns of work and elapsed time. 2 Identify the related formula This is the formula used for problems related to Power. \(\xpmhighlightbox{bgcolor=#D8F8FF, underlinecolor=#00758C, linestyle=dashed}{P}\, =\frac{\xpmhighlightbox{bgcolor=#F3E8FD, underlinecolor=#6232EC}{W}\, }{\xpmhighlightbox{bgcolor=#F3E8FD, underlinecolor=#6232EC}{t}\, }\) \(P\) = power \(W\) = work \(t\) = elapsed time 3 Input variables, solve and simplify Identify knowns\(W=60~\mathrm{J}\\ t=6~\mathrm{s}\)Plug-in values\(P=\frac{60~\mathrm{J}}{6~\mathrm{s}}\) Cancel terms that are in both the numerator and denominator \(P=\bm{10~}\mathrm{J}\bm{/}\mathrm{s}\)Convert units\(P=10~\mathrm{W}\) 4 Check unit of measurement power is measured in watts. Solution \(P=10~\mathrm{W}\)
10.If you push a wall and it doesn't move, work is not done as there is no displacement. When we hold a bag on our head and walk horizontally such that the angle between the displacement and the gravitational force is , thus, work done is zero.