3. There are many familiar situations in which the net force on a body is zero a

Question

3. There are many familiar situations in which the net force on a body is zero and yet the body moves with a constant velocity. One example is described below: A car traveling at constant speed on a straight road has the force of the road on the tires just balanced by the force of air friction. If the gas pedal is depressed further, the tires will push against the road harder and the road will push against the tires harder; so the car will accelerate forward – until the air friction builds up enough to balance the greater drive force Give another example of a body moving with constant velocity under balanced forces. Specify the cause of each force on the body and explain how these forces could be changed to affects the body’ motion.

Explanation / Answer

Let you hold a ball in your hand. Then weight of the ball will be balanced by the reaction force of your hand on the ball. Now suppose you start uplifting it with a constant velocity then due to constant velocity its acceleration of motion is zero and hence force acting on the ball is zero. But since the ball is still resting on your hand thus the reaction force on ball is still balanced by its weight.

And If you start uplifting it with a variable velocity then there we will be an unbalance of forces which we usually observe in day to day life by throwing of a ball upwards.

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