Multiple Choice Questions | Chapter 4 | Dynamics II | 9th Physics | National Book Foundation

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A seesaw balances perfectly with two children of equal weight sitting at equal distances from the fulcrum. If one child moves closer to the fulcrum:
(a) The seesaw remains balanced.
(b) The seesaw tips towards the child who moved closer.
(c) The seesaw tips towards the child who stayed further away.
(d) The seesaw topples.
When line of action of the applied force passes through its pivot point then moment of force acting on the body is:
(a) maximum (b) minimum (c) zero (d) infinite
If a body is at rest or moving with uniform rotational velocity, then torque acting on the body will be
(a) maximum (b) minimum (c) zero (d) infinite
A body in equilibrium must not have:
(a) speed (b) quantity of motion (c) velocity (d) acceleration
A uniform rotating fan is said to be in:
(a) static equilibrium only (b) dynamic equilibrium only
(c) both in static and dynamic equilibrium (d) not in equilibrium
You throw a weighted fishing net into a calm lake. As the net sinks, it opens fully underwater, spreading out its mesh evenly. Compared to the moment it left your hand, where is the net’s center of mass now?
(a) higher in the water column (b) lower in the water column
(c) At the same depth but slightly shifted horizontally (d) Unchanged from its position when thrown
A tightrope walker is carrying a long pole while walking across a rope. The stability of the walker is affected if the pole is
(a) long and placed vertically (b) long and placed horizontally
(c) short and placed vertically (d) short and placed horizontally
It is more difficult to walk on a slippery surface than on a nonslippery one because of:
(a) reduced friction (b) increased friction (c) high grip (d) lower weight
For an object moving with terminal velocity, its acceleration:
(a) increases with time (b) decreases with time
(c) is zero (d) first increases then decreases
The correct order o comparison for the terminal speeds of a raindrop, snowflake and hailstone is:
(a) raindrop snowflake hailstone (b) hailstone raindrop snowflake
(c) snowflake raindrop hailstone (d) raindrop = snowflake = hailstone
You are trying to loosen a nut using a spanner, but it is not working. In order to open the nut, you need to:
(a) Insert a pipe to increase length of spanner (b) use a spanner of small length
(c) use plastic and spanner (d) tie a rope with spanner
The force that always changes direction of velocity and not its magnitude is called:
(a) gravitational force (b) electric force (c) centripetal force (d) friction
The reason that a car moving on a horizontal road gets thrown out of the road while taking a turn is:
(a) the reaction of the ground (b) rolling friction between tyre and road
(c) gravitational force (d) lack of sufficient centripetal force
A car drives at steady speed around a perfectly circular track
(a) The car’s acceleration is zero (b) The net force on the car is zero
(c) Both the acceleration and net force on the car point outward
(d) both the acceleration and net force on the car point inward
A satellite of mass ‘m’ is revolving around the earth with an orbital speed ‘v’. If mass of the satellite is doubled, its orbital speed will become:
(a) double (b) half (c) one fourth (d) remain the same
Why long spanner is used to open or tight nuts of vehicle’s tyre? While tightening a small nut, extra-long wrench is not suitable. Why?
Why door knobs are fixed at the edge of door? What will happen it the door knob is at the middle of the door?
If you drop a feather and a bowling ball from the same height, which one will reach the terminal velocity first? Which one of them will hit the ground first?
Why do ice skates effortlessly slide on ice, while your shoes cause skidding?
Explain why it’s easier to push a car on flat tyres than inflated ones. What happens to the frictional force between the tyres and the road?
When standing on a crowded school bus, which stance would provide better stability and prevent you from being pushed over: legs joined or legs spread apart?
Why a moving bicycle is easier to balance? Relate this to the principles of rotational motion.
Why is a pencil standing on its tip unstable and what factors affect the stability of an object balanced on a point?
While driving what happens if the driver take the curve too fast? How does centripetal force play a role in keeping the car from skidding off the road?
Consider a situation where you swing a ball connected to a string in a circle. How does the tension in the string vary as the ball moves across different points in its circular path, and what forces are involved?
Why is it important for communication satellites in geostationary orbit to maintain a specific speed?