Motion in A Straight Line - Online Test

Answer : Option A
Explaination / Solution:

Average speed is the ratio of distance traveled to time spent. To find average speed, divide the total number of km traveled by the total elapsed time in hours. The answer is the average speed in km per hour.

Answer : Option A
Explaination / Solution:

Average speed is the absolute value of the average velocity or the magnitude of the velocity. Average Speed is always positive.

Answer : Option A
Explaination / Solution:

Instantaneous velocity is the velocity of an object in motion at a specific point in time. This is determined similarly to average velocity, but we narrow the period of time so that it approaches zero.

The formula for instantaneous velocity is the limit as t approaches zero of the change in position over the change in t.

Mathematically,

limt→0ΔxΔt

Where x is the given function with respect to time t. The Instantaneous Velocity is expressed in m/s.

Answer : Option B
Explaination / Solution:

Velocity is defined as the rate of change of position with respect to time, which may also be referred to as the instantaneous velocity to emphasize the distinction from the average velocity. In terms of a displacement-time (x vs. t) graph, the instantaneous velocity (or, simply, velocity) can be thought of as the slope of the tangent line to the curve at any point.

Answer : Option D
Explaination / Solution:

The principle is that the slope of the line on a position-time graph reveals useful information about the velocity of the object. If the velocity is constant, then the slope is constant (i.e., a straight line).

Answer : Option B
Explaination / Solution:

Position-time graph of horizontal straight line parallel to time axis represents that the position of the body does not changes with the passage of time. So it represents the rest state of motion. It means velocity of object is zero.

Answer : Option C
Explaination / Solution:

Acceleration is the rate of change of velocity with time.It is a vector quantity.

Average acceleration is the change in velocity per unit time over an interval of time.

Let initial velocity at time interval t​​​​​​1 is v​​​​​​1 and final velocity at time interval t​​​​​2 is v​​​​​​2

Then

a⃗ avg=Δv⃗ Δt=v⃗ 2−v⃗ 1t2−t1

Answer : Option B
Explaination / Solution:

instantaneous acceleration is measured over a "short" time interval. The word short in this context means infinitely small or infinitesimal — having no duration or extent whatsoever.

It's a mathematical ideal that can can only be realized as a limit. The limit of a rate as the denominator approaches zero is called a derivative.

Instantaneous acceleration is then the limit of average acceleration as the time interval approaches zero — or alternatively, acceleration is the derivative of velocity.

a=limt→0ΔvΔt=dvdt

Answer : Option A
Explaination / Solution:

Consider a particle moving along a straight line with uniform acceleration 'a'. At t = 0, let the particle be at A and vo be its initial velocity and when t = t, v be its final velocity.

Acceleration = Change in velocitytime taken

=>a=v−vot−0

=> at=v−vo

=> v=vo+at

Answer : Option C
Explaination / Solution:

initial velocity u = 60 m/s

As it stop final velocity v = 0

Time taken t = 4 s

We know,

a=v−ut

=0−604=−15 m/s2

Negative sign shows it is declaration.