Science Do as directed; [1 M ]

1. Speed (or Velocity)
2. Acceleration

Acceleration

1. The speedometer of a car measures instantaneous speed of the car.
2. Odometer is a device used to record the distance travelled by the car.

In addition to speed, we should know the direction in which the body is moving.

Motion of moon around the earth.

It represents uniform velocity.

Uniform circular motion.

Displacement Time graphs represent the change in the magnitude of a position vector of a particle with respect to its initial position over time. If it is straight line, parallel to the time axis, it represents that the position of the object does not change with respect to time. As the position does not change, the object is at rest. As the object remains at rest with respect to time, the velocity is zero.

Some examples of vector quantities include force, velocity, acceleration, displacement, and momentum.

When a body is moving with uniform velocity, its acceleration is zero.

When the body comes back to its starting point, it has zero resultant displacement but covers a certain non-zero distance.

The S.I. unit of both distance and displacement is metre.

Average velocity of a moving body can be zero.

None of the statement is true for displacement First statement is false because displacement can be zero. Second statement is also false because displacement is less than or equal to the distance travelled by the object.

Uniformly accelerated motion.

The tip of the ‘seconds’ hand’ of a watch represents uniform circular motion. It is an accelerated motion.

Acceleration

Speed.

Speed of a body in a specified direction is called velocity.

S.I. unit of retardation is m/s².

The area below velocity-time graph gives the distance covered by the object.

Negative acceleration is also called retardation.

The displacement is always zero when satellite makes a complete round along its circular path. It is because of the fact that initial and final positions coincide in one complete round.

When a body is moving with uniform velocity, its acceleration is zero.

The slope of a speed-time graph indicates acceleration.

The slope of a distance-time graph indicates speed.

The path of an object looks like line, zigzag line and curve etc.
Explanation:
Uniform motion refers only to speed of the object. Speed is described by distance traveled by an object with time. Uniform motion i.e. speed conveys no information regarding the direction of the object.
If object continues to move in fixed direction, then path will look like the straight line. Otherwise with varying direction & uniform motion, there could be various paths like straight line, zigzag line, circle, curve and many more.

The odometer of an automobile measures the distance covered by an automobile.

It represents uniform velocity.

The body has uniform speed.

It represents non-uniform acceleration.

Direction of motion.

The body is not moving. It is stationary.

The Speed of the body is constant or uniform.

When the object moves in a single straight line, the magnitude of average velocity equal to average speed.

The magnitude of average velocity of an object is equal to its average speed, only when an object is moving in a straight line.

When the body comes back to its starting point, it has zero resultant displacement but covers a certain non-zero distance.

No, because if a body takes a round trip such that its final position is same as the starting position, then the displacement of the body is zero but the distance travelled is non-zero.

Possible
When a ball is thrown up at maximum height, it has zero velocity, although it will have constant acceleration due to gravity, which is equal to 9.8m/ s².

Possible
When a car is moving in a circular track with constant speed, it is accelerating due to change in direction of motion.

Possible
A car is moving in a circular track, its acceleration is perpendicular to the direction of motion.

No, earth moves round the sun with uniform speed, but its velocity changes continuously.

Speed is a scalar quantity as it has magnitude only, it has no specified direction.

Distance is a scalar quantity.

Distance is considered as a scalar quantity because it shows only magnitude, there is not use of direction.