Exploring Forces — Quiz

Q1. For a force to come into play, at least how many objects must interact?

• A. One
• B. Two
• C. Three
• D. Four

Q2. A fielder hits a moving cricket ball with a bat, and the ball flies in a new direction. The force applied has primarily caused a change in

• A. Shape of the ball
• B. Mass of the ball
• C. Direction of motion of the ball
• D. Colour of the ball

Q3. Muscular force is produced when our muscles

• A. Stay stationary
• B. Change in colour
• C. Contract and elongate
• D. Become magnetic

Q4. Ravi pushes his geometry box once on a smooth glass top and once on a sandy floor with the same effort. On the sandy floor it stops sooner because

• A. Friction is greater on rough surfaces
• B. Friction is greater on smooth surfaces
• C. Gravity is greater on sand
• D. The geometry box becomes lighter on sand

Q5. Aeroplanes, ships and high-speed trains are designed with specific streamlined shapes mainly to

• A. Make them look attractive
• B. Reduce friction due to air or water around them
• C. Increase their weight
• D. Reduce their muscular force

Q6. When two suitable objects are rubbed against each other, static charges build up on their surfaces. These charges are called 'static' because

• A. They move at the speed of light
• B. They flow through metal wires
• C. They do not move by themselves
• D. They appear only in summer

Q7. Two balloons rubbed with the same woollen cloth are brought close to each other. What is observed?

• A. They attract each other
• B. They repel each other
• C. They stick together permanently
• D. They burst on contact

Q8. A ball thrown vertically upwards finally returns to the ground because

• A. The wind always pushes it down
• B. It loses its colour in air
• C. Gravity pulls it back towards the Earth
• D. Air becomes thicker at the top

Q9. The weight of an object on the Moon becomes about one-sixth of its weight on the Earth. The reason is

• A. The Moon's gravitational pull is much weaker than the Earth's
• B. The mass of the object becomes one-sixth on the Moon
• C. The Moon's air pressure is much higher
• D. The object becomes smaller on the Moon

Q10. An object placed in water sinks when

• A. The buoyant force is much larger than the gravitational force
• B. The two forces are exactly equal
• C. The gravitational force is larger than the buoyant force
• D. There is no gravitational force on the object

Q11. In Activity 5.5 two ring magnets are slid onto a vertical wooden stick with their like poles facing each other. The upper magnet floats above the lower one because

• A. Friction holds it up
• B. Like poles repel and the magnetic force balances its weight
• C. Gravity acts upwards on the upper magnet
• D. The stick exerts an electric force on the magnet

Q12. Priya's friend holds her moving bicycle from behind to stop it. The push the friend applies is an example of force used to

• A. Increase the speed of the bicycle
• B. Change the shape of the bicycle
• C. Stop or decrease the speed of the bicycle
• D. Pull the bicycle towards the Earth

Q13. A pair of bullocks ploughing a field and a horse pulling a cart both rely on

• A. Magnetic force of the animals
• B. Electrostatic force in their tails
• C. Muscular force of the animals
• D. Gravitational pull of the cart

Q14. When different objects are hung one by one from a spring, the spring stretches by different amounts. This shows that

• A. All objects have the same mass
• B. The spring does not work properly
• C. Different objects are pulled by the Earth with different forces
• D. The spring's length is fixed

Q15. Sonali says they must pedal harder while cycling against the wind. The wind makes pedalling harder because the wind exerts on the cyclist a

• A. Magnetic force in the forward direction
• B. Push opposite to the direction of motion
• C. Gravitational pull sideways
• D. Pull in the direction of motion