CHAPTER – 9- CLASS IX
NEWTON’S FIRST LAW OF MOTION:
Any object remains in the state of rest or in uniform motion along a straight line, until it is
compelled to change the state by applying external force.
Explanation: If any object is in the state of rest, then it will remain in rest untill a exernal force is
applied to change its state. Similarly an object will remain in motion untill any external force is
applied over it to change its state. This means all objects resist to in changing their state. The
state of any object can be changed by applying external forces only.
NEWTON’S FIRST LAW OF MOTION IN EVERYDAY LIFE:
a. A person standing in a bus falls backward when bus is start moving suddenly. This happens
because the person and bus both are in rest while bus is not moving, but as the bus starts
moving the legs of the person start moving along with bus but rest portion of his body has
tendency to remain in rest. Because of this person falls backward; if he is not alert.
b. A person standing in a moving bus falls forward if driver applies brakes suddenly. This
happens because when bus is moving, the person standing in it is also in motion along with bus.
But when driver applies brakes the speed of bus decreases suddenly or bus comes in the state
of rest suddenly, in this condition the legs of the person which are in the contact with bus come
in rest while the rest parts of his body have tendency to remain in motion. Because of this
person falls forward if he is not alert.
NEWTON’S FIRST LAW OF MOTION:
Any object remains in the state of rest or in uniform motion along a straight line, until it is
compelled to change the state by applying external force.
Explanation: If any object is in the state of rest, then it will remain in rest untill a exernal force is
applied to change its state. Similarly an object will remain in motion untill any external force is
applied over it to change its state. This means all objects resist to in changing their state. The
state of any object can be changed by applying external forces only.
NEWTON’S FIRST LAW OF MOTION IN EVERYDAY LIFE:
a. A person standing in a bus falls backward when bus is start moving suddenly. This happens
because the person and bus both are in rest while bus is not moving, but as the bus starts
moving the legs of the person start moving along with bus but rest portion of his body has
tendency to remain in rest. Because of this person falls backward; if he is not alert.
b. A person standing in a moving bus falls forward if driver applies brakes suddenly. This
happens because when bus is moving, the person standing in it is also in motion along with bus.
But when driver applies brakes the speed of bus decreases suddenly or bus comes in the state
of rest suddenly, in this condition the legs of the person which are in the contact with bus come
in rest while the rest parts of his body have tendency to remain in motion. Because of this
person falls forward if he is not alert.
