Unit test -3

KALAAFAANU SCHOOL

PHYSICS UNIT TEST -3

GRADE- 8

Max marks: 25 Time: 45 m

Name: -------------------------------------- Index: --------------- Class: --------

Instructions: Round up the correct option for multiple choice questions. (5 marks)

1. On the Earth, the gravitational field strength is 10 N/kg. On the Moon, the

gravitational field strength is 1.6 N/kg.

If an object has a weight of 50 N on Earth, what is its weight on the Moon?

A 1.6 N B 5.0 N C 8.0 N D 80N

2. The propeller on a boat pushes water backwards with a force of 2000 N. The boat moves through the water against a total resistive force of 1800 N.

According to Newton’s third law, what is the forward force on the propeller due to the water?

a) 3800 N

b) 2000 N

c) 1800 N

d) 200 N

Kalaafaanu School / Physics / Grade - 08 /Unit test -3 -2011

3. A steel spring is stretched by a load. The load is increased.

At first the extension is proportional to the load. The spring reaches its limit of proportionality at L.

4. When a body moves across a rough surface, a frictional force is produced.

Which statement about this force is always true?

A It acts in the direction of the motion.B It is equal in value to the force producing the motion.C It makes the body recoil in the opposite direction after stopping it.D It opposes the motion across the surface


5. A brick is placed on a Newton balance X and then on a beam balance Y.

What is measured by each balance?

Answer all the following questions

6. The weight of an astronaut on moon is 280 N and calculates his weight on the

earth. If the gravity on the surface of earth is 10 N/kg and the moon is 1.6 N/kg

Weight on the Earth ………………… [2]


7. A car has a mass of 800 kg. If the engine provides a forward force of 3600 N and

the total frictional force is 600 N

a. Calculate the acceleration of the car [2]

Acceleration of the car = …………… [2]

b. What happens to its acceleration when the forces are balanced

………………………………………………………………………………………

………………………………………………………………………………….. [1]

8. An Invalid in a wheel chair has a mass of 90 kg uses a force of 1600 N to move

forward for 6 s

a. Calculate the acceleration of Invalid

Acceleration of the car = …………… [2]

b. Calculation the distance travelled

Distance travelled = …………………… [2]


9. Use the data table to the right to answer this question. You will need a sheet of graph paper. The information represents the data recorded from a spring stretching experiment.

a) What is the unstretched length of the spring?

b)

Unstretched length ……………… [1]

c) Copy and complete the table [1]

d) Plot and graph of extension load graph [4]

e) Over which section of the graph line is the extension proportional to the load.Mark the letter with x. [1]

f) What load would produce a 55 mm extension [1]

………………………………………………………………………………...

g) What extension would produce when a force of 30 N is added [1]

…………………………………………………………………………………

Check your answers....


Load /N 0 1 2 3 4 5 6Length /mm 30 37 44 51 58 68 80

Extension /mm


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Unit test -3