Grade 8 Science — Forces: contact and non-contact

1.A ball is thrown straight up. Starting from The object moves straight up, put what happens next back into order.

• It stops momentarily at the top
• It falls back down, its speed increasing
• The object moves straight up
• Its speed goes on decreasing

2.A box is pushed to the right across a table. In which direction does friction act on it?

• a) Downwards, into the table
• b) Upwards, away from the table
• c) To the right, along with the push
• d) To the left, opposite to the way the box is moving

3.A spring balance measures up to 10 N, with a bigger mark at each newton. Which mark is at 6 N?

4.A 1 kg object weighs 10 N on the Earth, 25.4 N on Jupiter, 9 N on Venus and 3.8 N on Mars. What does the same object weigh on the Moon?

• a) 9 N
• b) 3.8 N
• c) 10 N
• d) 1.6 N

5.What is the SI unit of force called? Give the one word.

6.An object is carried to the Moon. Which of these changes, and which stays put?

• a) Its weight changes; its mass stays the same
• b) Its mass changes; its weight stays the same
• c) Neither changes
• d) Both change

7.The chapter explains why friction is greater on a rough surface. What is its explanation?

• a) Rough surfaces attract objects magnetically
• b) Rough surfaces are heavier than smooth ones
• c) Rough surfaces heat up faster, and heat resists motion
• d) Irregularities on the two surfaces lock into each other and oppose one sliding over the other

8.An object placed in a liquid floats rather than sinks. What does the chapter say about the two forces on it?

• a) The buoyant force and the gravitational force are equal
• b) The gravitational force is greater than the buoyant force
• c) There is no gravitational force acting on a floating object
• d) The buoyant force acts downwards and the gravitational force upwards