Edexcel PHYSICS Doubts

[The Golden Girl =D]

what about the first and last part of the graph (increase in V and decrease in V) ?

[dk bose]

Mr Astarmathsandphysics, could you please try my sum one more time,cause ur answer to it is wrong. the correct answer is 1.05m. plz cross check it with ur solution , its 4m the A2 physics revision guide.

[astarmathsandphysics]

Can you repost the question I got wrong

[dk bose]

here is the  question-
A ceiling fan is turning at a rate of 100 revolutions per minute. A spider
is clinging to a blade of the fan. If the spider experiences a centripetal
acceleration greater than 0.3g, it will lose its grip on the blade and be flung
off. How far from the centre of the fan can the spider safely go?

Plzz try it one more time and give the solutions as fast as possible.!!!!!

[astarmathsandphysics]

v^2/r>0.3g
r<v^2/0.3g
v=100/60*circumference of circle=(100/60)*2 pi r msince 100/60 revs per second
so r <(100/60 *2 pi r)^2/0.3g=37.3r^2 so r<1/37.3=0.027m

[dk bose]

Sir, its still not clear to me.you have to get the final answer as 1.05m.try it one more time. its becoming really hard for me to solve the sum. waiting for ur reply!!!

[astarmathsandphysics]

Is the book wrong?
Like the retarded cowboy who thought Iraq could destroy the world?

[dk bose]

Sir,its not joketime!!! i have doubts with which i have to deal as my exams are coming up.they are-
1)a racing car is moving at constant velocity along a track.explain how newton's first law is satisfied for this racing car.
2)Describe and explain how the resultant force on a skydiver varies from the moment they jump from a plane.
3)A person standing on a bus is thrown towards the rear of the bus as it starts to move forwards and to the front as it slows down.why?
 

[astarmathsandphysics]

1)forces balanced so no constant speed in straight line
2)Air reistance zero to start. It increases as the parachitist falls until it equals his weight and his velocity is constant. When he opens his chute air resistance increases suddenly so there is resultant upwards force and acceleration upwards until air resistance equals weight again and speed is constant.
3)Because the passenger has inertia - his body will resist any attempt to change its state of motion.

[dk bose]

some more doubts-
1)When a driving force is removed,a moving object 's drag will slow it down to a stop.This means it loses all its kinetic energy.explain how this disappearance of energy can be in keeping with the law of conservation of energy.
2)one way of storing surplus electrical energy from a power station is to use it to raise water from a lower reservoir to a higher one.This water can then be released to generate electricity again later.explain how this system might be limited by the law of conservation of energy.   

[astarmathsandphysics]

1)Because lost energy is used to overcome the friction force, and the kinetic energy is converted into heat via friction
2)Some of the energy input to raise the water is lost to friction, and some of the potential energy of the water is also lost to friction as it falls.

I like jokes, so you have to live with them.

[dk bose]

1)At Acapulco,divers jump from a cliff 36m high into the sea.At the base of the cliff there is a ledge which sticks out a distance of 6.4m.What must be the diver's minimum horizontal velocity in order to miss this ledge and enter the sea safely?

2)An aeroplane carrying out a parcel releases a parcel while travelling at a steady speed of 90m/s at an altitude of 200m.calculate:
a)th time between the parcel leaving the aeroplane and it striking the ground.
b)the horizontal distance travelled by the parcel in this time .
c)the speed at which the parcel strikes the ground.

[astarmathsandphysics]

here you are dk

[dk bose]

1)A hockey player passes the ball at 15m/s to a team mate who stops it completely in 0.1s.What force does the receiver's stick have to apply to the ball?

2)A penalty stroke is flicked from a distance of 6.40m from the goal line.The striker scoops it so that the ball leaves the ground at 45 degrees angle and a speed of 8m/s.How does the goalkeeper have to make a save before the ball crosses the goal line?

3)The study of mechanics in sport is a popular and often profitable new idea of scientific study. Descibe how a sport scientist could use ICT to collect data to study the movement of players and equipment overtime. Explain why technological developments have made the data collected more valid and reliable than with traditional methods of studying mechanics.

[astarmathsandphysics]

1)f*t=m*v Need to know the mass
2)I presume you mean to find the height
The horizontal speed is 8cos 45=5.656m/s
Use x=u_x t to find the time:t=x/u_x =6.4/5.656=1.132 s
now work vertically
s=?
u=8sin45=5.656
v=? (not needed)
a=-9.8
t=1.132 s
s=ut+1/2at^2 =5.656*1.132-1/2*-9.8*1.132^2=0.12m the ball crosses at a height of 0.12m

3)Fit all the players with trackers and take their position every second. Computers are more reilable and can gather and analyse data methodically.
3)