Physics Questions & Answers - Free Online Practice

4,061.

Calculate the refractive index of the material for the glass prism in the diagram above

^√2/₂

⁴/₃

√2

³/₂

View answer & explanation

Correct answer is C

n =	sin((A+D)/2)
	sin(A/2)

where A = the refracting angle of the prism(60^o)
D = angle of deviation of the ray (30^o)

n =	sin((60+30)/2)
	sin(60/2)

=	sin 45
	sin 30

=
¹/_√2/_¹/₂
^√2/₂/_¹/₂
= ^√2/₂ x ²/₁ = √2
n = √2

4,062.

The diagram above shows the force (F) acting on an object through a distance (x). The work done on this object is expressed as

Fx J

^Fx/₂ J

Fx² J

^F/_x J

View answer & explanation

Correct answer is B

The work done on this object is given by the area of the triangle, which is equal to ¹/₂ fx

4,063.

The diagram above show s the force-extension curve of a piece of wire. The energy stored when the wire is stretched from E to F is?

7.5 x 10^-3J

2.5 x 10^-3J

1.5 x 10^-2J

7.5 x 10^-1J

View answer & explanation

Correct answer is D

Energy store is equal to the work done in stretching the wire from E to F given by the area of the shaded trapezium under the graph.
= 1/2(0.1 x 0.2) x (0.1 - 0.05)
= 1/2(0.3) x 0.05
= 0.15 x 0.05
= 0.075
= 7.5 x 10-1J

4,064.

In the diagram above, determine the r.m.s current

31A

48A

60A

80A

View answer & explanation

Correct answer is B

I_r.m.s = ^V_r.m.s/_Z
But Z =
√ R² + X_L²

=
√ 4² + 3²

=
√ 16 + 9

=
√ 25

∴I_r.m.s = ²⁴⁰/₅
= 48.0A

4,065.

In the circuit diagram above , the ammeter reads a current of 3A when R is 5Ω and 6A when R is 2Ω. Determine the value of x

8Ω

2Ω

10Ω

4Ω

View answer & explanation

Correct answer is C

for a parallel R and X, when R = 5Ω,

effective resistance R =	5X
	5+X

and when R = 2Ω

effetive resistance R =	2X
	2+X

Thus since E = I(R+r), and if r = 0 then E = IR
∴(i) E = 3(5X/(5+x)); (ii) E = 6(2X(2+x))
∴3(5X/(5+X)) = 6(2X/(2+X))
=> (5X/(5+X)) = 2(2x/(2+X))
∴ (5X/(5+X)) = (4X/(2+X))
5x(2+x) = 4x(5+x)
10x + 5x2 = 20x + 4x2
5x2 - 4x2 = 20x - 10x
=>x2 = 10x
∴x2 - 10x = 0
x(x - 10) = 0
∴ x = 0 or 10
∴ x = 10Ω