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Section I- Force, Work, Energy and Power
- What are the forces acting on a box when it is pulled along a frictional surface?
- What are the forces acting on a moving rocket?
- Is mass conserved in a moving rocket?
- Two bodies A and B of mass 10kg and 15 kg are at rest. Which body will require greater force to start moving? Explain.
- What is the cause of acceleration in a body?
- State the energy changes that takes place in (i) Inverter (ii) Solar battery
- What is the SI unit of energy, momentum, Force?
- What is the physical quantity derived from the change of momentum?
- (a) What is the magnitude of the gravitational force that the Earth exerts on the Moon?
(b) What is the magnitude of the gravitational force that the Moon exerts on the Earth?
10. A sailboat is tied to a mooring with a line. The wind is from the southwest. Identify all the forces acting on the sailboat.
11. A box slides down an incline with uniform acceleration. It starts from rest and attains a speed of 2.7 m/s in 3.0 s. Find (a) the acceleration and (b) the distance moved in the first 6.0 s.
12. A rock is swung on the end of a rope in a horizontal circle at constant speed. The rope breaks. Immediately after the rope breaks, the ball will ________
13. A 40,000-kg freight car is coasting at a speed of 5.0 m/s along a straight track when it strikes a 30,000-kg stationary freight car and couples to it. What will be their combined speed after impact?
14. An ice skater is in a fast spin with her arms held tightly to her body. Explain why?
15. A 90-g ball moving at 100 cm/s collides head-on with a stationary 10-g ball. Determine the speed of each after impact if (a) they stick together, (b) the collision is perfectly elastic
16. Just before striking the ground, a 2.0-kg mass has 400 J of KE. If friction can be ignored, from what height was it dropped?
17. Compute the power output of a machine that lifts a 500-kg crate through a height of 20.0 m in a time of 60.0 s.
18. A 200-kg cart is pushed slowly up an incline. How much work does the pushing force do in moving the cart up to a platform 1.5 m above the starting point if friction is negligible?
- Weight of the body acting downwards, Normal reaction acting upward, pulling force, frictional force acting opposite to the direction of the pulling force.
- Drag, weight, thrust, resistance.
- No. Mass is not conserved in a moving rocket. The oxygen fuel depletes due to combustion resulting in the loss of overall mass of the rocket.
- The body with mass 15 kg will require greater force to make it move from rest. The body of 15kg mass will have more inertia than the body of 10 kg as inertia is a function of mass.
- A body is accelerated when an unbalanced force acts on the body and the body is not in equilibrium under different forces.
- (i) Electrical energy to chemical energy to electrical energy. (ii) Solar energy to electrical energy.
- Joule, Kgm/s, Newton.
- Force or impulse.
- Same in both cases a) and b) 1.98 × 1020 N
10. 1) the force of gravity; 2) the force of water opposing gravity and the force of water currents; 3) the force of the wind; 4) the force of the line tied to the mooring
- (a) 0.90 m/s2, (b) 16 m
12. move outward tangent to the circle from the point the rope broke
13. 2.9 m/s
14. Moment of inertia remains constant during the motion and the angular velocity is increased. With a full stretched arm, the frictional resistance was more and with the arms folded the resistance gets minimized.
15. (a) 90 cm/s, (b) 80 cm/s; 1.8 m/s
16. 20.0 m
17. 1.63 KW
18. 2.94 kJ
Section II- Light
- A ray of light travels through Light Flint glass to Crown Glass. Will the angle of refraction be greater than the angle of incidence? Explain.
- On what factors does the lateral shift of the light ray depend while it passes through a glass plate?
- Why does diamond glitter under light?
- Under which conditions the phenomena of total internal reflections occur?
- Why a glass beaker filled with glycerin gets disappeared when it is immersed in a beaker containing glycerin.
- A person standing in water sees his feet bent. Explain why?
- With angle of prism remaining constant, the angle of deviation will only depend on the angle of incidence. Justify the statement.
- Under what conditions will the angle of deviation be minimum?
- What is the use of fiber optics?
10. State the conditions on which the critical angle of a medium depend?
11. Light rays are travelling from Flexi glass to crown glass and incident at an angle greater than the critical angle but internal reflection is not observed. Explain?
12. Explain why white cloth washed with indigo appears whiter?
13. What is achieved by rotating the camera lens while capturing a photograph?
- The angle of refraction is lesser than the angle of incidence. The refractive index of crown glass is 1.52 whereas the refractive index of Light Flint glass is 1.58 and hence it is a denser medium. So the light will move closer to the normal while passing through light flint glass.
- The factors are the thickness of the glass plate and the angle of incidence of the light on the glass surface.
- Diamond is cut in such a way that the faces of the diamond act as prisms. Due to total internal reflection, the light rays get trapped inside the prism and have successive reflections inside the diamond which makes it glitter.
- Total internal reflections occur when a ray of light travels from a denser medium to a rarer medium and the angle of incidence becomes greater than the critical angle.
- This is phenomenon occurs due to equal refractive index of glass and glycerin. An object is visible only when some light after passing through it is reflected or refracted. But as the μ is almost equal the speed of light in both of them is equal making them act like a single body. Hence no reflection or refraction takes place.
- Assume that X is the tip of the foot immersed in water. The rays emerging from point X after coming to the surface are end away from the normal and come to the eyes of the observer giving the illusion that they are coming from point Y, located above X. Every point is likewise raised making it apparent as if the foot is bent as seen in the picture.
- i=for A to be constant, deviation will depend on the incident angle only.
- Hint: for this case i = e and r1 = r2.
- Fiber optics are used to transmit light signals over long distance. They work on the principle of total internal reflection.Read on to understand the principle
Fiber optics (optical fibers) are long, thin strands of very pure glass about the diameter of a human hair. They are arranged in bundles called optical cables and are used to transmit light signals over long distances. The parts of a single optical fiber are as follows:
Core– Thin glass center of the fiber where the light travels
Cladding– Outer optical material surrounding the core that reflects the light back into the core (like walls)
Buffer coating– Plastic coating that protects the fiber from damage and moisture
A fiber optic is so thin that it becomes extremely flexible even though it is made completely of glass. In a fiber optic, light enters one end and because its diameter is so small, the light is never able strike the inside walls at less than the critical angle, even when bent. This means that the light undergoes total internal reflection each time it strikes the wall of the fiber optic. Therefore, the light is only able to exit at the other end of the fiber. Fiber optic cables are used to carry telephone and computer communications. Fiber optics are advantageous to the user because they can carry much more information in a much smaller cable, have no interference from electromagnet fields and this results in “clearer” connections, have no electrical resistance, and there is no hazard of electrocution if a fiber optic cable breaks.
- Critical angle depends on color of the light, pair of media concerned ie, the wavelength of the light and the temperature of the medium.
- For internal reflection to occur, light rays have to travel from denser medium to lighter medium. Since crown glass is denser, total internal reflection will not occur.
- Indigo imparts a bluish tinge on the white cloth which reflects more light and appears whiter.
- The lens is adjusted so that the image is formed at the focal point of the lens.
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