Question

It is not so easy to cut an apple with a blunt knife. But the same apple can be cut very

easily with a sharp knife when the same force is applied. Why does this happen?

1 The area of contact between the apple and the sharp knife is much lower, so the pressure

applied is higher for the same force.

2 The force acting between the apple and the sharp knife is much higher than between the apple

and the blunt knife.

3 The weight of the blunt knife is more than that of the sharp knife and hence it becomes difficult

to cut.

4 The weight of the blunt knife is less than that of the sharp knife and hence it becomes difficult to

cut.

Science Test CLASS 8 SET NO 1

6

Q: 23

Air was blown into a balloon at the top of Mt. Everest and its mouth was tied with a

string. What would happen to the size of the balloon if it was brought down to sea

level, say directly to Mumbai?

1 It will become bigger for air pressure outside the balloon is now less than the pressure inside it.

2 It will reduce in size as air pressure outside the balloon is now more than air pressure inside it.

3 It will be the same as air pressure outside does not change much with altitude.

4 Can't say, it depends on the weather in Mumbai, whether it is experiencing high or low pressure.

Q: 24

Four friends were discussing about the direction in which air in the atmosphere exerts

pressure.

Here is what each one of them said.

Rafe: Air in the atmosphere exerts pressure only upwards from the Earth.

Jared: Air in the atmosphere exerts pressure only downwards towards the Earth.

Devin: Air in the atmosphere exerts pressure in all directions.

Shane: Air does not exert any pressure.

Who among them is right?

1 Rafe 2 Jared 3 Devin 4 Shane​

Answer 1

Answer:

1 The area of contact between the apple and the sharp knife is much lower, so the pressure. applied is higher for the same force. ... 3 The weight of the blunt knife is more than that of the sharp knife and hence it becomes difficult. to cut.

Explanation: