Question

Calculate the work required to be done to be done to stop a car of 1500kg moving at a velocity of 20m/s?​

Answer 1

Solution :

➡ Given:

✏ Mass of car = 1500 kg

✏ Initial velocity of car = 20 m/s

➡ To Find:

✏ Work required to be done to stop the car.

➡ Concept:

✏ This type of question can be solved by Work-Energy theorem.

✏ When Force and displacement are oppositely directed, the kinetic enegy of the body decreases.

✏ The decreases in K.E. us equal to the work done by the body against the retarding force.

➡ Formula:

✏ Relation between work done and change in kinetic energy is given by

$\star \: \underline{ \boxed{ \bold{ \rm{ \pink{W = \triangle{K.E.} = \frac{1}{2} m( {u}^{2} - {v}^{2} )}}}}} \: \star$

➡ Calculation:

✏ In this case, final velocity of car v = 0

$\mapsto \rm \: W = \frac{1}{2} \times 1500 \times ( {20}^{2} - {0}^{2} ) \\ \\ \mapsto \rm \: W = \frac{1}{2} \times 1500 \times 400 \\ \\ \mapsto \: \underline{ \boxed{ \bold{ \rm{ \orange{W =300 \: KJ }}}}} \: \star \star$

Answer 2

$\mathtt{\huge{\fbox{Solution :)}}}$

Given ,

• Mass (m) = 1500 kg
• Initial Velocity (u) = 20 m/s
• Final velocity (v) = 0 m/s

We know that , the change in kinetic energy is called work done

$\large \mathtt{ \fbox{Work \: done = \frac{1}{2}m \bigg( {(u)}^{2} - {(v)}^{2} \bigg)}}$

Substitute the known values , we get

$\sf \mapsto Work \: done = \frac{1}{2} \times 1500 \bigg( {(20)}^{2} - {(0)}^{2} \bigg) \\ \\ \sf \mapsto Work \: done = 750 \times 400 \\ \\ \sf \mapsto Work \: done = 300000 \\ \\ \sf \mapsto Work \: done = 300 \: \: Kilo \: joule$

Hence , the work done is 300 Kilo joule

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