Calculate the work required to be done to stop a car of 1500 kg moving at a velocity of 60 km/h?
Solution and Explanation
Initial velocity of the car \(u =\) \(60 \ km/h\)
\(u = \frac {60×1000}{60×60}\)
\(u= \frac {50}{3}\ ms^{-1}\)
Final velocity \(v = 0\) (object has to be stopped)
Initial kinetic energy \(= \frac 12×m×v^2\)
\(KE=\frac 12×1500×(\frac {50}{3})^2\)
\(KE = \frac {1500 \times 2500 \ }{2 \times 9}\)
\(KE= 208333.30\ J\)
Final kinetic energy \(= \frac 12×1500×0 = 0\)
Therefore,
Work done = change in kinetic energy = \(208333.30-0 = 208333.30\ J\)
Top Questions on Work
- In an actual regenerative Rankine cycle, the net work out put will be _____ as compared to simple Ranking cycle.
- A metal has work function \(w_0\) = 3.3×10-19 J. What should be the minimum frequency of the incident radiation that can remove an electron from the metal surface? [Given h = 6.6x10-34 J-s]
- In each of the following a force, F is acting on an object of mass, m. The direction of displacement is from west to east shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative, positive or zero.
- Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
• Suma is swimming in a pond.
• A donkey is carrying a load on its back.
• A wind-mill is lifting water from a well.
• A green plant is carrying out photosynthesis.
• An engine is pulling a train.
• Food grains are getting dried in the sun.
• A sailboat is moving due to wind energy. - An object of mass, m is moving with a constant velocity, v. How much work should be done on the object in order to bring the object to rest?
Questions Asked in CBSE Class IX exam
Use these adverbs to fill in the blanks in the sentences below.
awfully sorrowfully completely loftily carefully differently quickly nonchalantly(i) The report must be read ________ so that performance can be improved.
(ii) At the interview, Sameer answered our questions _________, shrugging his shoulders.
(iii) We all behave _________ when we are tired or hungry.
(iv) The teacher shook her head ________ when Ravi lied to her.
(v) I ________ forgot about it.
(vi) When I complimented Revathi on her success, she just smiled ________ and turned away.
(vii) The President of the Company is ________ busy and will not be able to meet you.
(viii) I finished my work ________ so that I could go out to play
- CBSE Class IX
- The fun they had
- Match the meanings with the words/expressions in italics, and write the appropriate meaning next to the sentence. The first one has been done for you.
1. I knew a man was following me, I was scared out of my wits. (very frightened)
2. I got a fright when I realised how close I was to the cliff edge.
3. He nearly jumped out of his skin when he saw the bull coming towards him.
4. You really gave me a fright when you crept up behind me like that.
5. Wait until I tell his story — it will make your hair stand on end.
6. Paralysed with fear, the boy faced his abductors.
7. The boy hid behind the door, not moving a muscle- CBSE Class IX
- The snake and the mirror
- How does the author describe: (i) his father, (ii) his mother, (iii) himself?
- CBSE Class IX
- My childhood
- What do you think his words mean? Why do you think he spoke those words?
- CBSE Class IX
- My childhood
A driver of a car travelling at \(52\) \(km \;h^{–1}\) applies the brakes Shade the area on the graph that represents the distance travelled by the car during the period.
Which part of the graph represents uniform motion of the car?- CBSE Class IX
- Graphical Representation of Motion
Concepts Used:
Work
Work is the product of the component of the force in the direction of the displacement and the magnitude of this displacement.
Work Formula:
W = Force × Distance
Where,
Work (W) is equal to the force (f) time the distance.
Work Equations:
W = F d Cos θ
Where,
W = Amount of work, F = Vector of force, D = Magnitude of displacement, and θ = Angle between the vector of force and vector of displacement.
Unit of Work:
The SI unit for the work is the joule (J), and it is defined as the work done by a force of 1 Newton in moving an object for a distance of one unit meter in the direction of the force.
Work formula is used to measure the amount of work done, force, or displacement in any maths or real-life problem. It is written as in Newton meter or Nm.