## Numericals from Newton’s Laws of motion based on F=ma (For calss XI students of Kendriya Vidyalaya Pattom)

Download the questions and solve them and submit on or before 9 Oct 2014

- A force acts for 10 s on a body of mass 10 kg after which the force ceases and the body describes 50 m in the next 5 s. Find the magnitude of the force. [Ans: 10 N]
- A truck starts from rest and rolls down a hill with constant acceleration. It travels a distance od 400 m in 20s. Calculate the acceleration and the force acting on it if its mass is 7 metric tonnes. [Ans: 2 m/s
^{2}, 14000N] - A motor car running aat the rate of 7 m/s can be stopped by applying brakes in 10 m. Show that total resistance to the motion, when the brakes are on is one fourth of the weight of the car.
- In an Xray machine, an electron is subjected top a force of 10
^{-23}N. In how much time the electron will cover a distance of 0.1 m,? Take the mass of the electron = 10^{-30}kg

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## Numericals from Newton’s Laws of motion based on F=ma (For calss XI students of Kendriya Vidyalaya Pattom)

Download the questions and solve them and submit on or before 9 Oct 2014

- A force acts for 10 s on a body of mass 10 kg after which the force ceases and the body describes 50 m in the next 5 s. Find the magnitude of the force. [Ans: 10 N]
- A truck starts from rest and rolls down a hill with constant acceleration. It travels a distance od 400 m in 20s. Calculate the acceleration and the force acting on it if its mass is 7 metric tonnes. [Ans: 2 m/s
^{2}, 14000N] - A motor car running aat the rate of 7 m/s can be stopped by applying brakes in 10 m. Show that total resistance to the motion, when the brakes are on is one fourth of the weight of the car.
- In an Xray machine, an electron is subjected top a force of 10
^{-23}N. In how much time the electron will cover a distance of 0.1 m,? Take the mass of the electron = 10-30 kg

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## How Stephen Hawking lived so long with ALS?

It is normally observed that a person with ALS (Amyotropic Lateral Sclerosis) succumbs to death within five years. Stephen Hawking‘s condition was first diagnosed when he was 21, and he was not expected to see his 25th birthday. But how he managed to “actively” to his 72 years of age? This is a matter to be discussed.

**What is ALS?**

ALS stands for Amyotropic Lateral Sclerosis and is a motor neuron disease. Also known as as Lou Gehrig’s disease after an American baseball first baseman who played 17 seasons in Major League Baseball (MLB) for the New York Yankees (1923–1939); and in 1995 Gehrig’s streak ended in 1939 after he was diagnosed with amyotrophic lateral sclerosis (ALS) which forced him to retire at age 36 and claimed his life two years later.

ALS is a neuro degenerative disease.

**What causes ALS?**

The exact cause of LAS is not known. 5% to 10% caused by a defective gene that prevents the body from producing a normal amount of an enzyme called superoxide dismutase. This enzyme helps neutralize free radicals — highly reactive oxygen molecules produced during metabolism and capable of damaging body tissues. Researchers speculate that defects in protective enzymes may also account for non-inherited ALS and that environmental toxins may be a factor.

Some evidence suggests that the disease may be triggered by exposure to heavy metals, animal hides, or fertilizers, although this is by no means proven. In addition, viral infection and severe physical trauma have been implicated as possible contributors. Other theories link ALS to a phenomenon called excitotoxicity, in which the nerve cells that control movement are overstimulated by a neurotransmitter called glutamate to the point where they eventually die.

**How ALS kills?**

Life expectancy turns on two things: the motor neurons running the diaphragm—the breathing muscles. So the common way people die is of respiratory failure. And the other thing is the deterioration of swallowing muscles, and that can lead to malnutrition and dehydration.

Stephen Hawking was predicted to leave this world at the age of 25, but now he is going to be 72! What made him live so long (Thank God!)?

Many account the round the clock medical care and the sophisticated environment to be responsible for his longevity.

But, the biological setup, the will power, the affirmation of self to go on to better heights despite the problems ….

**What do you think?**

Read More …

What is amyotrophic lateral sclerosis?

Who gets ALS?

What are the symptoms?

How is ALS diagnosed?

What causes ALS?

How is ALS treated?

What research is being done?

How Can I Help Research?

Where can I get more information?

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## Numerical Problems from “Uniform Circular Motion” –Online Home work for KV Pattom Class 11 students

All students of class XI are to copy down the questions and solve it in the home work copy and solve it to submit on or before 22 Sept 2014.

- What is the angular velocity of a second hand and minute hand of a clock?
- A body of mass 0.4 kg is whirled in a horizontal circle of radius 2 m with a constant speed of 10 ms . Calculate its (i) angular speed (ii) frequency of revolution (iii) time period and (iv) centripetal acceleration.
- A circular wheel of 0.50 m radius is moving with a speed of10 ms. Find the angular speed.
- Assuming that the moon completes one revolution in a circular orbit around the earth in 27.3 days, calculate the acceleration of the moon towards the earth. The radius of the circular orbit can betaken as 3.85 x 10 km.
- The angular velocity of a particle moving along a circle of radius 560 cm is increased in 5 minutes from 100 revolutions per minute to 400 revolutions per minute. Find angular acceleration and (ii) linear acceleration.
- Calculate the linear acceleration of a particle moving in a circle of radius 0.4 m at the instant when its angular velocity is 2 rad /s and its angular acceleration is 5 rad/s
^{2} - A threaded rod with 12 turns per cm and diameter 1.18 cm is mounted horizontally. A bar with a threaded hole to match the rod is screwed onto the rod. The bar spins at the rate of 216 rpm. How long will it take for the bar to move 1.50 cm along the rod.

## Projectile Motion – Numerical Problems (Assignment for KV Pattom Class XI students)

The students are requested to start solving these numerical problems. More questions will be added **till 8 pm on 13/09/2014.** There will be **more than 20 questions** in all. All students are expected to solve at least 20 numericals among these. The deadline form submission is 15/09/2014.

- A football player kick a ball at an angle of 37° to the horizontal with an initial speed of 15 m/s. Assuming that the ball travels in a vertical plane, calculate (i) the time at which the ball reaches the highest point. (ii) the maximum height reached by the ball (iii) the horizontal range of the projectile and (iv) the time for which the ball is in air.
- A body is projected with a velocity of 20 m/s in a direction making an angle 60° with the horizontal. CCalculate (i) position after 0.5 seconds and (ii) velocity after 0.5 seconds
- The maximum vertical height of a projectile is 10 m. If the magnitude of the initial velocity is 28 m/s, what is the direction of the initial velocity? (g=9.8 m/s
^{2 }) - A bullet fired from a gun with a velocity of 140 m/s strikes the ground at the same level as the gun at a distance of 1 km. Find the angle of inclination with the horizontal at which the bullet is fired. (g=9.8 m/s
^{2 }) - A bullet is fired at an angle of 15° with the horizontal and hits the ground 6 km away. Is it possible to hit a target 10 km away by adjusting the angle of projection assuming the initial speed to be the same?
- A cricketer can throw a ball to a maximum horizontal distance of 160 m. Calculate the maximum vertical height to which he can throw the ball. (g=10 m/s
^{2 }) - A football is kicked with 20 m/s at a projection angle of 45°. A receiver on the goal line 25 metres away in the direction of the kick runs the same instant to meet the ball. What must be his speed, if he is to catch the ball before it hits the ground?
- A bullet fired at an angle of 60° with the vertical hits the ground at a distance of 2 km. Calculate the distance at which the bullet will hit the ground when fired at an angle of 45°, assuming the speed to be the same.
- A person observes a bird on tree 39.6 m high and at a distance of 59.2m. With what velocity the person should shoot an arrow at an angle of 45° so that it may hit the bird?
- A ball is thrown from the top of a tower with an initial velocity of 10 m/s at an angle of 30° with the horizontal. If it hits the ground at a distance of 17.3 m from the base of the tower, calculate the height of the tower. (Given g =10 m/s
^{2 }) - Prove that the time of flight T and the horizontal range R of a projectile are connected by the equation gT
^{2}=2R tanθ, where θ is the angle of projection. - Show that the range of a projectile for two angles α and β is same if α+β=90°
- A body is projected with velocity of 40 m/s. After 2 s it crosses a vertical pole of height 20.4 m. Calculate the angle of projection and horizontal range.
- A plane is flying horizontally at a height of 1000 m with a velocity of 100 m/s when a bomb is released from it. Find (i) the time taken by it to reach the ground. (ii) the velocity with which the bomb hits the target and (iii) the distance of the target.
- From the top of a building 19.6 m high a ball is projected horizontally. After how long does it strike the ground? If the line joining the point of projection to the point where it hits the ground makes an angle of 45° with the horizontal, what is the initial velocity of the ball.
- A body is thrown horizontally from the top of a tower and strikes the ground after 2 seconds at an angle of 45° with the horizontal. Find the height of the tower and the speed with which the body was thrown. Take g =9.8 m/s
^{2 }) - A ball is projected horizontally from a tower with a velocity of 4 m/s. Find the velocity of the ball after 0.7 s. (Given g =10 m/s
^{2 }) - In between two hills of heights 100 m and 92 m respectively , there is a valley of breadth 16m. If a vehicle jumps from the first hill to the second, what must be the minimum horizontal velocity so that it may not fall into the valley? (Given g =10 m/s
^{2 }) - A mailbag is to be dropped into a post office from an aeroplane flying horizontally with a velocity of 270 km/h at a height of 176.4 m above the ground. How far must the aeroplane be from the post office at the time of dropping the bag so that the bag directly falls into the post office?
- An aeroplane is flying in a horizontal direction with a velocity of 600 km/h and at a height of 1960 m. When it is above a point A on ground an object is dropped from it. The object strike the ground at the point B. Find the distance AB.
- Two tall buildings are situated 200 m apart. With what speed must a ball be thrown horizontally from the window 540 m above the ground in one building so that it will enter a window 50 m above the ground in the other?

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