According to third law of motion when we push on an object, object pushes back on us with an equal a

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8. FORCE AND LAWS OF MOTION

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According to the third law of motion when we push on an object, the object pushes back on us with an equal and opposite force. If the object is a massive truck parked along the roadside, it will probably not move. A student justifies this by answering that the two opposite and equal forces cancel each other. Comment on this logic and explain why the truck does not move.

Option A

Option B

Option C

Option D

Solution

The truck has a large mass. Therefore, the static friction between the truck and the road is also very high. To move the car, one has to apply a force more than the static friction. Therefore, when someone pushes the truck and the truck does not move, then it can be said that the applied force in one direction is cancelled out by the frictional force of equal amount acting in the opposite direction. Therefore, the student is right in justifying that the two opposite and equal cancel each other.

Standard 9

Science

A $8000 \,kg$ engine pulls a train of $5$ wagons, each of $2000 \,kg$, along a horizontal track. If the engine exerts a force of $40000\, N$ and the track offers a friction force of $5000\, N$, then calculate: the net accelerating force(in $N$).

easy

A stone of $1\, kg$ is thrown with a velocity of $20\, m\ s^{-1}$ across the frozen surface of a lake and comes to rest after travelling a distance of $50\, m$. What is the force of friction(in $N$) between the stone and the ice?

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Two persons manage to push a motorcar of mass $1200\, kg$ at a uniform velocity along a level road. The same motorcar can be pushed by three persons to produce an acceleration of $ 0.2\, m \,s^{-2}$ . With what force(in $N$) does each person push the motorcar? (Assume that all persons push the motorcar with the same muscular effort.)

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The following is the distance-time table of an object in motion:

Time in seconds Distance in metres

$0$ $0$

$1$ $1$

$2$ $8$

$3$ $27$

$4$ $64$

$5$ $125$

$6$ $216$

$7$ $343$

$ (a)$ What conclusion can you draw about the acceleration? Is it constant, increasing, decreasing, or zero?

$(b) $ What do you infer about the forces acting on the object?

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How much momentum will a dumb-bell of mass $10\, kg$ transfer to the floor if it falls from a height of $80\, cm$ ? Take its downward acceleration to be $10\, m \,s^{-2}.$

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Time in seconds	Distance in metres
$0$	$0$
$1$	$1$
$2$	$8$
$3$	$27$
$4$	$64$
$5$	$125$
$6$	$216$
$7$	$343$

Solution

Similar Questions

A $8000 \,kg$ engine pulls a train of $5$ wagons, each of $2000 \,kg$, along a horizontal track. If the engine exerts a force of $40000\, N$ and the track offers a friction force of $5000\, N$, then calculate: the net accelerating force(in $N$).

A stone of $1\, kg$ is thrown with a velocity of $20\, m\ s^{-1}$ across the frozen surface of a lake and comes to rest after travelling a distance of $50\, m$. What is the force of friction(in $N$) between the stone and the ice?

How much momentum will a dumb-bell of mass $10\, kg$ transfer to the floor if it falls from a height of $80\, cm$ ? Take its downward acceleration to be $10\, m \,s^{-2}.$

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