Physics questions and answers

Physics Questions and Answers

If you want to learn more about the nature and properties of matter and energy or you're simply preparing for a Physics exam, these Physics past questions and answers are ideal for you.

271.

A lead bullet of mass 0.05kg is fired with a velocity of 200ms\(^{-1}\) into a block of mass 0.95kg. Given that the lead block can move freely, the final kinetic energy after impact is?

A.

50J

B.

100J

C.

150J

D.

200J

Correct answer is A

Given 
m\(_{1}\) = 0.05kg, u\(_{1}\) = 200ms\(^{-1}\), m\(_{2}\) = 0.95kg

K.E = \(\frac{1}{2}\)m\(_{r}\)v\(^{2}\)

m\(_{1}\)u\(_{1}\) = v(m\(_{1}\) + m\(_{2}\)) [law of conversation of momentum]

v = \(\frac{0.05 \times 200}{0.05 + 95}\) = 10ms\(^{-1}\)

K.E = \(\frac{1}{2}\)(1)10\(^{2}\) = 50J

 

272.

Particles of mass 10\(^{-2}\)kg is fixed to the tip of a fan blade which rotates with angular velocity of 100rad\(^{-1}\). If the radius of the blade is 0.2m, the centripetal force is?

A.

2N

B.

20N

C.

200N

D.

400N

Correct answer is B

Given 
m = 10\(^{-2}\)
w = 100rads\(^{-1}\)
F = mw\(^{2}\)r
r = 0.2m
F = ?

= 10\(^{-2}\) x (100)\(^{2}\) x 0.2

= 20N

273.

Two bodies have masses in the ratio3:1. They experience forces which impart to them, acceleration in the ratio 2:9 respectively. Find the ratio of forces the masses experienced

A.

1:4

B.

2:1

C.

2:3

D.

2:5

Correct answer is C

Given \(\frac{m_{1}}{m_{2}} = \frac{3}{1}\) \(\Rightarrow\) m\(_{1}\) = 3m\(_{2}\)

\(\frac{a_{1}}{a_{2}} = \frac{2}{9}\) = a\(_{1}\) = \(\frac{2a_{2}}{9}\)

\(\frac{F_{1}}{F_{2}}\) = ?

Since F = ma

\(\Rightarrow\)  \(\frac{F_{1}}{F_{2}} = \frac{m_{1}a_{1}}{m_{2}a_{2}}\) = \(\frac{(3 \not m_{2})(2 \not a_{2})}{\not m_{2} a_{2} \not a_{3}}\)

\(\frac{F_{1}}{F_{2}} = \frac{2}{3}\) \(\Rightarrow\) 2:3

274.

The inner diameter of a test tube can be measured accurately using a?

A.

micrometer screw gauge

B.

pair of dividers

C.

meter rule

D.

pair of vernier calipers

Correct answer is D

Vernier calipers are also used to measure the internal and external diameters of a tube

275.

A certain radioactive source emits radiation that was found to be deflected by both magnetic and electric fields. The radiation is?

A.

beta rays

B.

gamma rays

C.

x-rays

D.

ultra-violet rays

Correct answer is A

 Both the electric field and magnetic field affect the β-particles.