Work and Energy — Flashcards
Gujarat Board · Class 9 · Science
25 flashcards for Work and Energy (Gujarat Board Class 9 Science) to test yourself on key terms and facts. Sample: "What are the two conditions that must.
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What are the two conditions that must be satisfied for work to be done according to the scientific definition?
Answer
For work to be done scientifically: (1) A force should act on an object, and (2) The object must be displaced in the direction of the force. If either condition is missing, no work is done.
Define work done by a constant force and write its formula.
Answer
Work done by a constant force is equal to the product of force and displacement in the direction of force. Formula: W = F × s, where W = work done, F = force applied, s = displacement in the direction…
What is the SI unit of work? Define 1 joule.
Answer
The SI unit of work is joule (J) or newton metre (N m). 1 joule is the amount of work done on an object when a force of 1 N displaces it by 1 m along the line of action of the force.
When is work done considered positive and when is it negative?
Answer
Work done is positive when the force and displacement are in the same direction (angle = 0°). Work done is negative when the force and displacement are in opposite directions (angle = 180°).
A force of 15 N acts on an object and displaces it by 10 m in the direction of force. Calculate the work done.
Answer
Given: F = 15 N, s = 10 m. Using W = F × s, Work done = 15 × 10 = 150 J. The work done is 150 joules.
Define energy and state its relationship with work.
Answer
Energy is the capacity or ability of an object to do work. An object having energy can exert force on another object and transfer energy to it. The unit of energy is the same as work (joule), since en…
What is kinetic energy? Write its formula and define the terms.
Answer
Kinetic energy is the energy possessed by an object due to its motion. Formula: Ek = ½mv², where Ek = kinetic energy, m = mass of the object, v = velocity of the object. It increases with speed.
An object of mass 2 kg is moving with velocity 5 m/s. Calculate its kinetic energy.
Answer
Given: m = 2 kg, v = 5 m/s. Using Ek = ½mv², Kinetic energy = ½ × 2 × (5)² = ½ × 2 × 25 = 25 J. The kinetic energy is 25 joules.
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