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All questions of September Week 2 for JEE Exam

If the slope of line m = tan 0°. Therefore, the line is …… to the X-axis.
  • a)
    Perpendicular
  • b)
    Parallel
  • c)
    Con current
  • d)
    Co-incident
Correct answer is option 'B'. Can you explain this answer?

Knowledge Hub answered
Slope of x-axis is m = tan 0° = 0.
 Since the inclination of every line parallel to x-axis is 0°, so its slope (m) = tan 0° = 0. Therefore, the slope of every horizontal line is 0.

The tangent of the angle which the part of the line above the X-axis makes with the positive direction of the X-axis is:
  • a)
    Perpendicular line
  • b)
    Slope of a line
  • c)
    Concurrent line
  • d)
    Parallel line
Correct answer is option 'B'. Can you explain this answer?

Preeti Iyer answered
The gradient or slope of a line (not parallel to the axis of y) is the trigonometrical tangent of the angle which the line makes with the positive direction of the x-axis. Thus, if a line makes an angle θ with the positive direction of the x-axis, then its slope will be tan θ.

Can you explain the answer of this question below:
The points A and B have coordinates (3, 2) and (1, 4) respectively. So, the slope of any line perpendicular to AB is
  • A:
    2
  • B:
    1
  • C:
    -1
  • D:
    -2
The answer is b.

Geetika Shah answered
If the lines are perpendicular to each other then their slopes are in the form m1.m2 = -1.(since product of slopes of two perpendicular lines is -1) Therefore , m = 1.

 Which is untrue about orbital velocity?
  • a)
    increases with the increase in height of satellite
  • b)
    depends on mass and radius of planet around which it revolves
  • c)
    it is independent of mass of satellite
  • d)
    decreases with an increase in radius of orbit
Correct answer is option 'A'. Can you explain this answer?

Om Desai answered
The untrue statement about orbital velocity is:

1. increases with the increase in height of satellite

Explanation: Orbital velocity is the speed at which an object revolves around a planet or other celestial body in a stable orbit. According to the equation for orbital velocity, v = √(GM/r+h), where G is the gravitational constant, M is the mass of the planet, and r is the radius of the orbit.

As the height of the satellite increases (meaning it gets far to the planet), its h increase , so reasulting in decrease in velocity .

The other statements are true:

2. depends on mass and radius of planet around which it revolves: As mentioned in the equation, orbital velocity depends on both the mass (M) of the planet and the radius (r) of the orbit.

3. it is independent of mass of satellite: The mass of the satellite does not appear in the equation for orbital velocity, so it does not affect the speed at which the satellite orbits the planet.

4. decreases with an increase in radius of orbit: From the equation, we can see that as the radius of the orbit (r) increases, the orbital velocity (v) decreases.

mand m2 are the slope of two perpendicular lines, if
  • a)
    m1.m2 = 1
  • b)
    m1= m2
  • c)
    m+ m2 = 0
  • d)
    1 + m1.m2 = 0
Correct answer is option 'D'. Can you explain this answer?

Lakshmi Roy answered
Explanation:

Two lines are perpendicular if the product of their slopes is -1. So, if m1 and m2 are the slopes of two perpendicular lines, then:

m1.m2 = -1

Rewriting this equation, we get:

1/m1 . 1/m2 = -1

Multiplying both sides by m1.m2, we get:

m2/m1 + m1/m2 = 0

This can be simplified as:

m1.m2 = 0

Therefore, the correct answer is option D.

A satellite which appears to be at a fixed position at a definite height to an observer is called:
  • a)
    Geostationary satellite and geosynchronous satellite
  • b)
    Polar satellite
  • c)
    Geostationary satellite
  • d)
    Geosynchronous satellite
Correct answer is option 'A'. Can you explain this answer?

Neha Joshi answered
As the relative velocity of the satellite with respect to the earth is zero, it appears stationary from the Earth surface and therefore it is called is geostationary satellite or geosynchronous satellite.

Two lines are said to be parallel when the difference of their slopes is
  • a)
    -1
  • b)
    0
  • c)
    1
  • d)
    2
Correct answer is option 'B'. Can you explain this answer?

Aryan Khanna answered
Parallel lines and their slopes are easy. Since slope is a measure of the angle of a line from the horizontal, and since parallel lines must have the same angle, then parallel lines have the same slope and lines with the same slope are parallel.

Slope of a line is not defined, when q = ……
  • a)
    60°
  • b)
    90°
  • c)
    30°
  • d)
    45°
Correct answer is option 'B'. Can you explain this answer?

Neha Sharma answered
Since tan θ is not defined when θ = 90°, therefore, the slope of a vertical line is not defined. i.e., slope of y-axis is m = tan 90° = ∞ i.e., not defined.

Kepler’s second law states that the straight line joining the planet to the sun sweeps out equal areas in equal time. The statement is equivalent to saying that:
  • a)
    longitudnal acceleration is zero
  • b)
    total acceleration is zero
  • c)
    transverse acceleration is zero
  • d)
    radial acceleration is zero
Correct answer is option 'C'. Can you explain this answer?

Suresh Reddy answered
According to the second law the orbital radius and angular velocity of the planet in the elliptical orbit will vary. The planet travels faster when closer to the Sun, then slower when farther from the Sun. Hence we can say that the transverse acceleration is zero while radial and longitudinal accelerations are not zero.

A satellite moves in a circular orbit around earth. The radius of this orbit is one half that of moon’s orbit. The satellite completes one revolution in:
  • a)
    (2) 3/2 lunar month
  • b)
    (2) 3 lunar month
  • c)
    (2) -3/2 lunar month
  • d)
    (2)1/2 lunar month
Correct answer is option 'C'. Can you explain this answer?

Suresh Reddy answered
We know that the time period of revolution for any object in orbit of radius r is 3
T = 2π (r3 / Gm) 1/2
Where m is the mass of earth.
As the ratio of radius of orbit of satellite to that of moon is 1:2
Hence there time period has a ratio of 1: 23/2

Different planets have different escape velocities because:
  • a)
    different planets have different atmosphere
  • b)
    they have different distances from sun
  • c)
    escape velocity depends on the body that has to escape the atmosphere of the planet
  • d)
    they have different masses and sizes
Correct answer is option 'D'. Can you explain this answer?

Nitin Nair answered
The formula for calculating the escape velocity from the surface of a celestial body (e.g. a planet) is:
where G is the universal gravitation constant, M is the planet’s mass and R is its radius.Different planets have different mass and radius - and therefore different escape velocity.

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