WAEC Physics Past Questions & Answers - Page 55

271.

Two forces 100N and 60N act on an object of mass 10kg as illustrated in the diagram above. Neglecting friction, calculate the acceleration of the object.

A.

4.0\(ms^{-2}\)

B.

13.4\(ms^{-2}\)

C.

16.0\(ms^{-2}\)

D.

22.6\(ms^{-2}\)

Correct answer is B

Resolving 100N into horizontal and vertical 

100 sin45 = 0.7071 * 100 = 70.71

100cos45 = 70.71

Vertical forces = 100 - 70.71 → 29.29

Horizontal force = 70.71 + 60 → 130.71

Resultant of vertical and horizontal forces using pythagoras thoerem

Resultant force (F) = m * a 

a = F/m → 133.9/10

a = 13.4 

272.

Which of the following statements about matter is not correct?

A.

Molecules of solids move more freely than molecules of liquids and gases

B.

Molecules of solids are more closely packed than those of liquids

C.

Energy is required to break the intermolecular forces of attraction between molecules

D.

Molecules of liquids move about within the liquid and they are in constant motion

Correct answer is A

All other properties of the different states of matter holds except that the molecules of solids don't move freely due to the fact that the particles in the solids are closely packed so it inhibits free motion.

273.

A body accelerates uniformly from rest at 2\(ms^{-2}\). Calculate its velocity when it has travelled a distance of 9m.

A.

3.0\(ms^{-1}\)

B.

4.5\(ms^{-1}\)

C.

6.0\(ms^{-1}\)

D.

18.0\(ms^{-1}\)

Correct answer is C

Given that \(u = 0ms^{-1}, a = 2ms^{-2}, s = 9m\)

We can use the equation, \(v^{2}=u^{2} +2as\) so that we have,

\(v^{2} = 0^{2} + 2\times 2\times 9\)

\(v^{2} = 36; v= 6.0ms^{-1}\)

Note; u = Initial velocity

v = final velocity

a = acceleration

s = distance covered

274.

Which of the following is the dimension for impulse?

A.

MLT\(^{-1}\)

B.

MLT\(^{-2}\)

C.

MLT

D.

ML

Correct answer is A

Impulse = Force \(\times\) time

Force has the dimension \(\frac{ML}{T^{2}}\), hence 

Impulse= \(\frac{ML}{T^{2}} \times T = \frac{ML}{T}\)

275.

The diagram above is a micrometer screw gauge. Determine its reading

A.

2.44mm

B.

2.46mm

C.

2.86mm

D.

2.96mm

Correct answer is B

No explanation has been provided for this answer.