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. If three persons are randomly selected , whats the probability that two were born on Monday and the other on Tuesday?
2. If Jack studies for tmr's test the prob. of getting a pass is 4/5 , if he doesnt study for it , the prob of getting a pass is 1/10. Given the prob. for Jack to study the test is 7/8 , find the prob. that he will fail the test .
1.The probability for Steven to hit the basket in a basketball shot is 0.4. If Steven makes three basketball shots find the probability of hitting two shots.
2. There are 5 res balls , 3 green balls amd 2 white balls in a bag . If two balls are drawn at random one by one with replacement,fins the probability that
(a) one red ball and one white ball are draen
(b) the two balls are same in colour
3. On average, David can answer correctly 2 questions out of 5,and Amy can answer correctly 1 out of 3 . If they attempt the same question separately , whats the probability of having the question solved?
Which of the following descriptions about ideal gas is correct?
(a) An ideal gas obeys the Boyle's Law only at high temperature and low pressure.
(2) The molecules of an ideal gas has no size.
(3) The internal energy of an ideal gas consists of KE only.
Guys please tell me the answer with explanation. Thanks very much !
1. A bullet of 0.2 kg travelling horizontally with a speed of 300 ms-1 hits a stationary wooden block of 5kg on a smooth table and is then embedded into it . They travel with the same speed after collision which lasts for 0.05s.
(a) find the final common speed.
(b) Find the depth that the bullet penetrates into the block.
2. A particle of mass 1kg travelling with speed 4ms-1 is collided by another particle of mass 0.2 kg travelling in the same direction with speed 5ms-1. If the 0.2 kg particle reverses direction with speed of 1 ms-1 after collision and the collision time is 0.1 s.
(a) Find the speed of the 1kg particle.
(b) Calculate the force acting on the 1kg particle during collision.
seems like the answer used by cosine or sine formula is different
Shouldn't the answer be the same in no matter situations?
5. A 500 g ball collides normally to a smooth wall with a speed of 5m/s. The ball rebounds at a speed of 4 m/s after collision which lasts for 0.4 s .
(a) Find the force acting on the wall by the ball.
(b) Repeat (a) if the ball collides with a smooth ground instead.
6 A spacecraft of mass 500 kg is travelling in space with a speed of 30 m/s. In order to accelerate to 50 m/s , an engine of mass 100 kg is ejected at the back of the aircraft.
(a) find the ejected velocity of the engone.
(b) Calculate the KE change of the ejection and briefly account for the change .
7. A 4 kg ball moving with speed of 3 m/s undergoes a head-on collision with a stationary ball of mass 2kg. Find the final speeds of the balls.
1. The density of nitrogen at s.t.p (i.e., 273K and 1atm) is 1.25 kg m^-3
(a) find the density of nitrogen at a temperature of 25 degree C and 1atm.
(b) Calculate the root mean square speed of nitrogen molecules at 25 degree C.
2. A vessel of volume 50 cm cube contains hydrogen at a pressure of 1 Pa and at a temperature of 27 ddegree C. Given the mass of one mole of hydrogen molecules is 2g.
(a) calculate the root mean square speed.
(b) find the total internam energy of the gas.
(c) if 0.05 mJ of heat is given to the gas with the volume fixed, find the new temperature , in degree C of the gas.
3. Explain the following fact about ideal gas in molecular terms.
The pressure can be kept constant if the temperature is increased while the volume is increased too.
1.A ball of mass 2 kg travelling with a velocity of 4 m/s at 45 degree hits the smooth ground in 4s as shown below.
(a)What are the forces acting on the ball during collision?
(b)(i) Assume the collision is elastic. What is the speed of the ball after collision?
(ii) What should be the horizontal component of the final velocity of the ball? Why?
(iii) Calculate the force acting on the ground by the ball during collision.
2.A rubber is dropped vertically onto a 80g trolley originally moving with 3m/s. The final common speed is 1.6m/s. Given that it takes 1 s for the rubber to rest on the trolley.
(a) Find the mass of the rubber,
(b) Find the internal force acting on the rubber during collision and state the physical origin of the force.
3. Two balls of same mass of 2kg are travelling with velocities of 2m/s due east and 3m/s due north initially. At a certain instant, they collide with each other and stick together. The collision time is 0.5s.
(a)Find the total common velocity of the particle by drawing a momentum vector diagram.
(b)Find the change of KE of the system .
4. The velocity of a ball of mass 3kg after being hit by wall changes from 4m/s due east to 3m/s due north in 5s. Find the force exerted on the wall by the ball during collision.
1. It is proposed to place a communications satellite in a circular orbit around the equator at a height of 3.59*10^7 m above the earth's surface.
(a) Find the period of revolution of the satellite in hrs . Take the radius of the earth as 6.14*10^6.
(b) What is the weight of a 50 kg astronaut inside the satellite? explain why he would feel 'weightless' in the satellite. Also explain whether he would have the same experience when falling freely back to the earth's in his capsule just prior to re-entry in the earth's atmosphere.
2. Calculate the weight of a 1kg mass at a distance of 2R from the centre of the earth, where R is the earth's radius.
3. Assume the moon takes 27.3 days to move once round the earth. Take the radius of the earth as 6.4*10^6 m. Estimate the distance between the centres of the Earth and the moon. State the assumption of your calculation.
4.(a) Describe the change in apparent weight of an object as it moves from the North Pole to the equator and finally to the South Pole.
(b) By assume the earth;s radius as 6.37*10^6 m , find the percentage difference of the apparent weight of a 1kg mass when weighting at pole and at equator. State assumptions made in ur calculations.