Questions
In which direction does force of friction act?
- Upward direction
- Downward direction
- The direction opposite to motion
- The direction of motion
Why it is advised to apply machine oil or grease in the moving parts of a machine at regular intervals?
- To increase wearing by increasing friction
- To give it a shiny appearance
- To prevent wearing by decreasing friction
- To prevent wearing by increasing friction
It is difficult to drag a bucket full of water than an empty bucket because
- force of friction decreases as we drag a bucket full of water
- force of friction increases with the increase of normal force due to increased weight
- force of friction increases with the decrease of normal force due to increased weight
- force of friction is independent of the weight of the body
Why is the shape of an aeroplane designed in a manner similar to the shape of a bird?
- To increase fluid friction
- To reduce fluid friction
- To maintain fluid friction
- To eliminate friction completely
Why is lubricating oil used in the chain of a bicycle?
- To reduce friction
- To increase friction
- To produce excess heat
- To make it less energy efficient
Friction cannot be increased by
- providing better contact
- decreasing roughness
- increasing normal force
- both (1) and (2)
In which of the following activities does friction not play any role?
- Walking on a road
- Writing with a pen
- Reading a book
- Production of fire by striking a matchstick
What is the frictional force exerted by fluids called?
- Upthrust
- Sliding friction
- Drag
- Thrust
Why are brake pads used in the brake system of bicycles and automobiles?
- To reduce friction
- To increase friction
- To reduce normal force
- To prevent wearing of wheels
Which of the following is the cause of friction between two surfaces?
- The force of attraction between the two surfaces in contact
- The interlocking of the irregularities of the surfaces in contact
- The force of repulsion between the two surfaces in contact
- The gravitational pull of the earth on the two surfaces
If your cycle is cleaned and oiled regularly, it will run smoothly and will last longer. Why?
- It increases friction in moving parts of the cycle.
- It reduces friction in moving parts of the cycle.
- It increases heating in the parts of the cycle.
- Both (1) and (3)
Which of the following statements is incorrect?
- Fluid friction can be minimised by giving suitable shapes to bodies moving in fluids.
- The soles of shoes and tyres of vehicles are treaded to decrease friction.
- In many machines, friction is reduced by using ball bearings.
- It is always easier to roll than to slide a body over another.
Even a child can pull a piece of luggage fitted with rollers as compared to the one without rollers. Why?
- Because rolling friction is greater than the sliding friction
- Because rolling friction is smaller than the sliding friction
- Because rolling friction is equal to the sliding friction
- Because rolling friction and sliding friction oppose each other
On which of the following factors does frictional force not depend?
- The nature of surfaces in contact
- The state of smoothness of two surfaces in contact
- How hard the two surfaces press together
- The size of the contact area
Why do we slip, when we accidently step on a banana peel?
- Because of increased friction
- Because of reduced friction
- Because of reduced gravitational force
- Because of upward reaction