1. Friction opposes the _______ between the surfaces in contact with each other.
2. Friction depends on the _______ of surfaces.
3. Frcition produces _______
4. The sprinkling of powder on the carrom board _______ friction.
5. Sliding friction is _______ than the static friction.
1. Friction opposes the relative motion between the surfaces in contact with each other.
2. Friction depends on the nature of surfaces.
3. Friction produces heat.
4. The sprinkling of powder on the carrom board reduces friction.
5. Sliding friction is less than static friction.
Choose the correct arrangement.
(a) rolling, static, sliding
(b) rolling, sliding, static
(c) static, sliding, rolling
(d) sliding, static, rolling
Answer: (c) static, sliding, rolling
(а) wet marble floor, dry marble floor, newspaper, and towel.
(b) newspaper, towel, dry marble floor, wet marble floor.
(c) towel, newspaper, dry marble floor, wet marble floor.
(d) wet marble floor, dry marble floor, towel, newspaper
Answer: (a) wet marble floor, dry marble floor, newspaper, and towel.
Fig. Frictional force is acting opposite to the movement of book i.e. upwards.
Answer: Soapy floor reduces the frictional force applied by the floor to the maximum. That is why it is difficult to walk on a soapy floor.
Answer: Sportsmen use shoes with a spike to increase the friction so, that their shoes do not slip while they run or play.
Answer: Seema will experience more frictional force because the heavy object will be pressed hard against the opposite surface and produces more friction.
Answer: Suppose a box kept on the surface has to be pushed. If the box is slid then, when the box starts sliding, the contact points on its surface do not get enough time to lock into the contact points on the floor. So the sliding friction is slightly less than the static friction and we find it easier to move the box already in motion than to get it started (i.e., static friction.)
Answer: Friction is a friend because:
• It allows us to walk comfortably on the ground.
• It allows us to grip and catch different objects.
• Things don’t move from their places because of friction.
• Speeds of moving objects can be minimized or stopped by friction only.
Friction is a foe because:
• It wears out materials, whether they are screws, ball- bearings, or soles of shoes.
• It also produces heat, which increases the wear and tear of machine parts. It also causes much wastage of energy, because this heat is not utilized.
Answer: When objects move through fluids, they have to overcome friction acting on them. In this process. They lose energy. To minimize friction, objects are given special shapes.
Answer: When brakes are applied frictional force acts on the vehicle which slows down the motion of the vehicle and finally brings it to rest.
Answer: A ball moving on the ground stops after some time because the ground applies a force of friction, which slows down the motion of the ball, and finally the ball stops.
Answer: Force of friction opposes the relative motion between two surfaces in contact and it acts on both surfaces.
4. What is spring balance?
Answer: Spring balance is a device used for measuring the force acting on an object.
5. How is the force measured by spring balance?
Answer: Spring balance consists of a coiled spring which gets stretched when a force is applied to it. Stretching of the spring is measured by a pointer moving on a graduated scale. The reading on the scale gives the magnitude of the force.
Answer: It is easier to hold a kulhar than a glass tumbler as the glass tumbler surface is smooth and provides lesser friction.
Answer: It would become more difficult to hold a glass tumbler with a film of cooking oil on its surface because this surface will provide no friction or least friction.
Why is friction called evil?
Answer: Friction is evil. It causes a lot of problems for us. It wears out the objects or materials on which it acts. The soles of our shoes get worn due to friction. The floors, machines, their parts, clothes, metals, etc. get worn due to the friction they bear. Friction spoils the parts of the machines. They are, therefore, regularly lubricated to minimize friction. Friction produces heat, which further damages the objects on which it is exerted, The grooves of the tires are finished due to regular friction they bear, which is offered by their regular motion on roads. Except for this wear and tear, friction utilize a large amount of energy spent to overcome it.
Answer: The sole of the shoe is grooved to provide the shoes better grip on the floor so that we can move safely.
10. What is rolling friction?
Answer: When one body rolls over the surface of another body, the resistance to its motion is called rolling friction.
Answer: Rolling reduces friction.
Answer: Wheels have reduced friction and it becomes easier to take things from one place to another.
Answer: The frictional force exerted by fluids is called drag.
Answer: Yes, the air has friction.
Answer: Yes, both the airplane and bird have streamlined bodies to minimize the force of friction provided by air while flying in the sky.