1

Two cars moving in the same direction have speeds of 100 kmh^{-1} and 130 kmh^{-1} what is the velocity of the faster car as measured by an observer in the slower car?

A

30 kmh^{-1}

B

130 kmh^{-1}

C

200 kmh^{}

D

230 kmh^{-1}

CORRECT OPTION:
a

Since the cars are moving in the same direction, the velocity of a body A, V_{a},relative to another body B, V_{b} is given by V = V_{a} - V_{b}

∴ the velocity of faster car is measured by the observer in the slower car is V = 130kmh^{-1} - 100 kmh^{-1} = 30 kmh^{-1}

∴ the velocity of faster car is measured by the observer in the slower car is V = 130kmh

2

A stone and a feather are dropped from the same height above the earth surface. ignoring air resistance, which of the following is correct?

A

the feather will be brown away by the wind while stone will drop steadily

B

the stone and the feather will both reach the ground a the same time

C

the feather will reach the ground first

D

the stone will reach the ground first

CORRECT OPTION:
b

The acceleration of free fall due to gravity is independent of mass of the body. Therefore, ignoring air resistance, which affects feather more than the stone, the stone and the feather will both reach the ground at the same time

3

A car moves with an initial velocity of 25 ms^{-1} and reaches a velocity of 45 ms^{-1} in 10s. what is the acceleration of the car?

A

2 ms^{-2}

B

5 ms^{-2}

C

20 ms^{-2}

D

25 ms^{-2}

CORRECT OPTION:
a

Acceleration = (increase in velocity)/time taken

= (45 - 25)/10 = (20)/10 = 2ms^{-2}

= (45 - 25)/10 = (20)/10 = 2ms

4

The surfaces of conveyor belts are made rough so as to

A

protect them while carrying loads

B

prevent the loads from slipping

C

enable them to carry more load

D

make them stronger

CORRECT OPTION:
b

Rough surface promotes friction. Therefore, roughness of conveyor belt prevents the load from slipping

5

A machine of velocity ratio 6 requires an effort of 400 N to raise a load of 800 N through I m. Find the efficiency of the machine

A

55. 6 %

B

50.0%

C

33.3%

D

22.2%

CORRECT OPTION:
c

Efficiency = (MA)/V.R x 100% = (load)/Effort x (1)/V.R

= (800)/400 x (1)/6 x 100% = 33.3%

= (800)/400 x (1)/6 x 100% = 33.3%

6

If a wire 30 cm long is extended to 30.5 cm by a force of 300 N. find the strain energy of wire

A

0.75 J

B

7.50 J

C

75.00 J

D

750.00 J

CORRECT OPTION:
a

Energy stored in a stretched wire (strain energy)

= average force x extension

= (1)/2 Fe

= (1)/2 x 300 N (30.5 - 30.0) x 10^{-2} m

= (300)/2 x 0.5 x 10^{-2} = 0.75J

= average force x extension

= (1)/2 Fe

= (1)/2 x 300 N (30.5 - 30.0) x 10

= (300)/2 x 0.5 x 10

7

In a hydraulic press, the pump piston exerts a pressure of 100 pa on the liquid. what force is exerted in the second piston of cross sectional area 3 m^{2}?

A

300 N

B

200 N

C

150 N

D

100 N

CORRECT OPTION:
a

Thrust = pressure x area = 100 pa x 3 m^{2} = 300 N

8

The accurate measurement of the relative density of a substance in its powdered form is done with a beam balance and

A

a density bottle

B

an eureka can

C

a pipette

D

a burette

CORRECT OPTION:
a

Since relative density = mass of substance

mass of equal volume of water relative density bottle should be used to determine the mass of the substance, and mass of an equal volume of water by filling the bottle with the powder and water respectively and weighed with the beam balance.

mass of equal volume of water relative density bottle should be used to determine the mass of the substance, and mass of an equal volume of water by filling the bottle with the powder and water respectively and weighed with the beam balance.

9

A hydrometer is an instrument used in measuring

A

vapour pressure of a fluid

B

density of liquid

C

relative humidity of a liquid

D

relative density of a liquid

CORRECT OPTION:
d

The instrument used in measuring relative density is hydrometer

10

One special advantage of alcohol over mercury as a thermometric liquid is its

A

low density

B

low freezing point

C

high specific

D

low boiling point

CORRECT OPTION:
b

The low freezing point of alcohol, -115°c enable low temperatures to be measured. mercury freezes at 39°c, and cannot be used in countries like Russia where winter temperatures of -40°c are common

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