Force:
A push or pull that tends to change the state of a body. An object will move from its position when a force is applied to it.
Rest:
When there is no change in its position with respect to time then object is in rest.
Motion:
When an objects position changes with respect to time iscalled motion.
Relative phenomenon:
An object can appear to be moving for one person, while it seems to be stationary for another.
Types of motion:
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S. No
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Type of motion
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What is it?
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Example
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1.
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Linear motion
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The object moves along a straight line.
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A car travelling in straight road.
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2.
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Circular motion
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The object travels in a circular path.
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Movement of artificial satellite orbiting the earth.
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3.
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Periodic or oscillatory motion
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Objects that are in repeated motion for equal intervals of time.
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The pendulum of a clock.
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Distance:
The total length of a path taken by an object to reach from one point to another is called distance. The SI unit of distance is metre (m) and it is a scalar quantity
Displacement:
The shortest distance from the initial to the final position of an object is called displacement. The SI unit of displacement is metre (m) and it is a vector quantity.
Uniform motion - equal distances in equal intervals of time
Non-uniform motion - unequal distances in equal intervals of time
Speed:
Speed is defined as the distance travelled by an object in unit time. The SI unit of speed is metre per second. This is represented by the symbol \(m s^{–1}\) (or) \(m/s\) and it is a scalar quantity.
\(speed\ =\ \frac{Total distance travelled}{Time taken}\)
\(v\ =\ \frac{s}{t}\)
Velocity:
Velocity is the rate of change in displacement. The speed of an object moving in a definite direction is known as velocity. Hence, it is a vector quantity. Its SI unit is (m s^{–1}\) (or) \(m/s\)
\(Velocity\ =\ \frac{Total displacemrnt}{Time taken}\)
Zero Displacement: If the initial and final point of an object's place is the same value, then the displacement is zero. Since there is no change in the position of an object, there is no displacement.
Acceleration:
A physical quantity called acceleration is the rate of change of velocity. In general, it is the increase in the velocity of an object with respect to time. The SI unit of acceleration is \(ms^−2\) and it is a vector quantity.
\(acceleration\ =\ \frac{change in velocity}{Time taken}\)
\(acceleration\ =\ \frac{v\ -\ u}{t}\)
Types of acceleration:
- Positive acceleration - velocity of an object increases with respect to time
- Negative acceleration - velocity of an object acts opposite to the direction of motion