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Laws of Motion

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Physics Part I

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Physics

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Class 10 Class 12

An automobile travelling with speed of 60 km/h, can brake to stop within a distance of 20 cm. If the car is going twice as fast, i.e 120 km/h, the stopping distance will be

  • 20 m

  • 40 m

  • 60 m

  • 80 m


D.

80 m

Third equation of motion gives
v2 = u2 + 2as ⇒ 2
s ∝ u (since v = 0)
where a = retardation of body in both the cases

therefore, straight s subscript 1 over straight s subscript 2 space equals space fraction numerator straight u subscript 1 superscript 2 over denominator straight u subscript 2 superscript 2 end fraction .... (i)

Here, s1 = 20 m, u1 = 60 km/h, u2 = 120 km/h. Putting the given values in eq. (i), we get

20 over straight s subscript 2 space equals space open parentheses 60 over 120 close parentheses squared
space straight s subscript 2 space equals space 20 space straight x space open parentheses 120 over 60 close parentheses squared
space equals space 20 space straight x space 4 space
space equals space 80 space straight m

Third equation of motion gives
v2 = u2 + 2as ⇒ 2
s ∝ u (since v = 0)
where a = retardation of body in both the cases

therefore, straight s subscript 1 over straight s subscript 2 space equals space fraction numerator straight u subscript 1 superscript 2 over denominator straight u subscript 2 superscript 2 end fraction .... (i)

Here, s1 = 20 m, u1 = 60 km/h, u2 = 120 km/h. Putting the given values in eq. (i), we get

20 over straight s subscript 2 space equals space open parentheses 60 over 120 close parentheses squared
space straight s subscript 2 space equals space 20 space straight x space open parentheses 120 over 60 close parentheses squared
space equals space 20 space straight x space 4 space
space equals space 80 space straight m

168 Views

What is Aristotle’s law of motion?

Aristotle’s law of motion states that an external force is required to keep the body in motion.
2445 Views

Is Aristotle’s law of motion now correct?

No. Aristotl'e law of motion is false. 
1233 Views

When the branches of an apple tree are shaken, the apples fall down. Why?

The apple fall from an apple tree when it shaken because of inertia of rest. Apple is in a state of rest and when the tree is suddenly shaken, apples still tends to remain in it's same state of rest whereas branches move. 

So, the apples fall down. 
1475 Views

Define inertia.

The property by virtue of which the body cannot change its state of rest or uniform motion in a straight line, unless an external force is acting on the body is called as Inertia. 
1316 Views

State Galileo’s law of motion.

Galileo’s law of motion states that, a body continues to move in the same direction with constant speed, if no force is acting on the body. 
1332 Views