Physics Test 150

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Physics Test 150

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Weekly Quiz Competition

Question 1
4 / -1

On an open ground, a motorist follows a track that turns to his left by an angle of 60° after every 500 m. Starting from a given turn, the displacement of the motorist at the third turn is

A
500 m

B
500√3 m

C
1000 m

D
1000√3 m

Solution

The path followed by the motorist is a regular hexagon ABCDEF of side 500 m, as shown in the given figure. Let the motorist starts from A and takes the third turn at D.

Therefore, the magnitude of this displacement is

AD = AG + GD = 500 m + 500 m = 1000 m
Question 2
4 / -1

A person moves 30 m north, then 30 m east, then 30√2 m south-west. His displacement from the original position is:

A
zero

B
28 m towards south

C
10 m towards west

D
15 m towards east

Solution

Resolving displacement 30√2 m south-west into two rectangular components, we get

Displacement in south

∴ Effective displacement due to 30 m north and 30 m south is zero.

Also effective displacement due to 30 m east and 30 m west in zero.
Question 3
4 / -1

The (x, y, z) coordinates of two points A and B are given respectively as (0, 4, -2) and (-2, 8, -4). The displacement vector from A to B is:

A

B

C

D

Solution
Question 4
4 / -1

A bird flies from (-3m, 4m, -3m) to (7m, -2m, -3m) in the xyz- coordinates. The bird's displacement vector is given by

A

B

C

D

Solution
Question 5
4 / -1

What is the dimensional formula for the universal gravitational constant

A
M^-1L³T^-2

B
M^-1L³T^-1

C
M^-1L²T^-2

D
None of the above

Solution

Calculation:

Force = G × m₁ × m₂ × [r²]^-1

⇒ G = Force × r² × [m₁ × m₂]^-1 --- (1)

Where, G = Universal Gravitational Constant

Now, the dimensions of,

Mass = [M¹ L⁰ T⁰] --- (2)

Radius (distance) = [M⁰ L¹ T⁰] --- (3)

Force = [M¹ L¹ T^-2] --- (4)

On substituting equation (2), (3) and (4) in equation (1) we get,

Universal Gravitational Constant = Force × r² × [m₁ × m₂]^-1

⇒ G = [M¹ L¹ T^-2] × [M⁰ L¹ T⁰]² × [M¹ L⁰ T⁰]^-1 × [M¹ L⁰ T⁰]^-1 = [M^-1 L³ T^-2].

Therefore, the Universal Gravitational Constant is dimensionally represented as [M^-1 L³ T^-2].
Question 6
4 / -1

Four girls skating on circular ice ground of radius 200 m start from a point P on the edge of the ground and reach a point Q diametrically opposite to P following different paths as shown in figure. For which girl displacement is equal to the actual length of path?

A
A

B
B

C
C

D
D

Solution
Question 7
4 / -1

A particle starts moving from point (2, 10, 1). Displacement for the particle is The final coordinates of the particle is

A
(10, 8, 2)

B
(8, 10, 2)

C
(2, 10, 8)

D
(8, 2, 10)

Solution
Question 8
4 / -1

Planck's constant has the same unit as:

A
force × time

B
force × speed

C
force × distance × time

D
None of the above

Solution

Force × distance = work done
The unit of work done is Joule.
Therefore the unit of
Force × distance × time = Joule × second
This is the same unit as Planck's constant.

So, the correct option is Force × distance × time
Question 9
4 / -1

The SI unit of work function of a metal used in photoelectric effect is

A
joule (J)

B
newton (N)

C
pascal (Pa)

D
hertz (Hz)

Solution

Work function: It is the minimum amount of energy required to cause photo-emission of electrons from a metal surface when light is incident on it.

The work function is also known as the threshold energy.
The energy of the incident light is equal to the sum of the work function and the photoelectron kinetic energy.
Therefore, the total energy of photon = work function + maximum kinetic energy of the electron.

The energy of a photon is given by the equation:

E = ℎν

Where ν is the frequency of incident light and h is the Planck's constant.

The work function is a measure of energy. All forms of energy have the same SI unit i.e. joule (J).
Question 10
4 / -1

What is the SI unit of electrical resistance?

A
Mole

B
Volt

C
Ohm

D
None of these

Solution

The SI unit of electrical resistance is Ohm (Ω) and it is the SI derived unit of electrical resistance, named after German physicist, Georg Simon Ohm.