Physics Test 159

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Physics Test 159

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Weekly Quiz Competition

Question 1
4 / -1

The terminal velocity of a copper ball of radius 5 mm falling through a tank of oil at room temperature is 10 cm s^-1. If the viscosity of oil at room temperature is 0.9 kg m^-1 s^-1, the viscous drag force is:

A
4.23 × 10^{− 6} N

B
8.48 × 10⁻³ N

C
8.48 × 10⁻⁵ N

D
4.23 × 10⁻³ N

Solution
Question 2
4 / -1

If a soap bubble expands, the pressure inside the bubble

A
Decreases

B
Increases

C
Remains the same

D
Is equal to the atmospheric pressure

Solution
Question 3
4 / -1

A spherical ball is dropped in a long column of a highly viscous liquid. The curve in the graph shown, which represents the speed of the ball (v) as a function of time (t) is

A
A

B
B

C
C

D
D

Solution

Initial speed of ball is zero and it finally attains terminal speed
Question 4
4 / -1

Read the assertion and reason carefully to mark the correct option out of the options given below:

Assertion: Young's modulus for a perfectly plastic body is zero.

Reason: For a perfectly plastic body, restoring force is zero.

A
If both assertion and reason are true and the reason is the correct explanation of the assertion.

B
If both assertion and reason are true but reason is not the correct explanation of the assertion.

C
If assertion is true but reason is false.

D
If the assertion and reason both are false.

Solution

Young's Modulus= (restoring force per unit area)/(elongation of wire/length of wire) now for a plastic body the restoring force is zero and it ultimately makes the Young's modulus zero. Hence both assertion and reason are true
Question 5
4 / -1

Read the assertion and reason carefully to mark the correct option out of the options given below:

Assertion : Stress is the internal force per unit area of a body.

Reason : Rubber is less elastic than steel.

A
If both assertion and reason are true and the reason is the correct explanation of the assertion.

B
If both assertion and reason are true but reason is not the correct explanation of the assertion.

C
If assertion is true but reason is false.

D
If the assertion and reason both are false.

Solution

Stress is defined as internal force (restoring force) per unit area of a body. Also, rubber is less elastic than steel, because restoring force is less for rubber than steel.
Question 6
4 / -1

A steel rod 2.0 m long has a cross-sectional area of 0.30 cm² . It is hung by one end from a support, and a 550-kg milling machine is hung from its other end. Determine the resulting strain. Young's Modulus of Steel (Y) = 20×10¹⁰ Pa

A
8.0 × 10⁻⁴

B
10.0 × 10⁻⁴

C
7.0 × 10⁻⁴

D
9.0 × 10⁻⁴

Solution

Stress = F⟂/A = (Mass x Acceleration⟂)/Cross-sectional Area

= (550 kg x 9.8 m/s²)/ (0.30×10−4 m²)

= 1.8×10⁸ Pa

Young's ModulusSteel (Y) = 20×10¹⁰ Pa = Stress/Strain

=> Strain = Stress/Y = 1.8×108 Pa / 20×10¹⁰ Pa

= 9.0×10⁻⁴
Question 7
4 / -1

A piece of copper having a rectangular cross-section of 15.2 mm × 19.1 mm is pulled in tension with 44,500 N force, producing only elastic deformation. Calculate the resulting strain? Take Young's modulus of copper as 42 × 10⁹Pa

A
3.65 × 10^-8

B
3.65 × 10^-3

C
3.65 × 10^-9

D
3.65 × 10^-2

Solution

Given Data,

Length of the piece of copper = l = 19.1 mm = 19.1 × 10^-3m

Breadth of the piece of copper = b = 15.2 mm = 15.2× 10^-3m

Tension force applied on the piece of cooper, F = 44500N

Area of rectangular cross section of copper piece,

Area = l× b

⇒ Area = (19.1 × 10-3m) × (15.2× 10-3m)

⇒ Area = 2.9 × 10^-4 m²

Modulus of elasticity of copper from standard list, η = 42× 10⁹ N/m2

By definition, Modulus of elasticity, η = stress/strain
Question 8
4 / -1

A 200-kg load is hung on a wire with a length of 4.00 m, a cross-sectional area of 0.200 × 10⁻⁴ m², and a Young’s modulus of 8.00 × 10¹⁰N/ m². What is its increase in length?

A
4.80 mm

B
4.70 mm

C
4.90 mm

D
4.60 mm

Solution

Mass, m = 200 kg

Length, L = 4 m

Cross-sectional area, A = 0.2 x 10^-4m²

Young's modulus, Y = 8 x 10¹⁰ N/m²

Increase in length = FL/AY

= mgL/AY

= 200*9.8*4/(0.2 x 10^-48 x 10¹⁰)

= 0.0049 m

= 0.49 cm

= 4.9 mm
Question 9
4 / -1

If the elastic limit of copper is 1.5 × 10⁸ N/ m², determine the minimum diameter a copper wire can have under a load of 10.0 kg if its elastic limit is not to be exceeded.

A
1.012 mm

B
0.912 mm

C
0.712 mm

D
0.812 mm

Solution
Question 10
4 / -1

A circular steel wire 2.00 m long must stretch no more than 0.25 cm when a tensile force of 400 N is applied to each end of the wire. What minimum diameter is required for the wire?

A
1.4 mm

B
10 mm

C
1.5 mm

D
12.4 mm

Solution

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Physics Test 159

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Physics Test 159

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Question 1

4.23 × 10− 6 N

8.48 × 10−3 N

8.48 × 10−5 N

4.23 × 10−3 N

Solution

Question 2

Decreases

Increases

Remains the same

Is equal to the atmospheric pressure

Solution

Question 3

A

B

C

D

Solution

Question 4

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

Solution

Question 5

If both assertion and reason are true and the reason is the correct explanation of the assertion.

If both assertion and reason are true but reason is not the correct explanation of the assertion.

If assertion is true but reason is false.

If the assertion and reason both are false.

Solution

Question 6

8.0 × 10−4

10.0 × 10−4

7.0 × 10−4

9.0 × 10−4

Solution

Question 7

3.65 × 10-8

3.65 × 10-3

3.65 × 10-9

3.65 × 10-2

Solution

Question 8

4.80 mm

4.70 mm

4.90 mm

4.60 mm

Solution

Question 9

1.012 mm

0.912 mm

0.712 mm

0.812 mm

Solution

Question 10

1.4 mm

10 mm

1.5 mm

12.4 mm

Solution

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4.23 × 10^{− 6} N

8.48 × 10⁻³ N

8.48 × 10⁻⁵ N

4.23 × 10⁻³ N

8.0 × 10⁻⁴

10.0 × 10⁻⁴

7.0 × 10⁻⁴

9.0 × 10⁻⁴

3.65 × 10^-8

3.65 × 10^-3

3.65 × 10^-9

3.65 × 10^-2