a) the work done by the pump.
b) The power rating the pump if its efficiency is 40%. (g= 10m/s²).
2) A Machine raises a load of 750 N through a height of 16m in 5 seconds. Calculate the power at which the machines works.
3) The world record for weigh-lifting is held by lakshya of India. He lifted 261kg to a height of 2.3m in 4s. Find
a) the weight lifted by Lakshya
b) the work done by him
c) the power developed by him (g= 10m/s²)
4) A book of mass 2kg is lifted from the floor to a shelf= 210cm above the floor.
a) What is the gravitational potential energy relative to the floor?
b) What is the gravitational potential energy relative to the head of a 165cm tall person. (g= 9.8 m/s²)
5)a) If a higher body and a heavier body have equal momentum, which will have more KE ?
b) If a lighter body and a heavy body have equal KE, which will have more momentum ?
6) A person mass of 85 kg swings from a tree on the end of a vine. His feet touch the ground 4m below the tree.
a) How fast is the person moving when he reaches the ground ? g=10 m/s²
b) Does your answer depend on person mass ? If yes, give reason.
c) Does your answer depend on the length of the vine ?
7) A body, when acted upon by a force of 10 kgf, gets displaced by 0.5m. Calculate the work done by the force when displacement is:
a) in the direction of force
b) at an angle of 60° to the force
c) normal to the force g= 10N/kg
8) a body P has a mass of 20 kg and is moving with a velocity of 5 m/s. Another body Q has a mass of 5 kg and is moving with a velocity of 20 m/s. Find the ratio of their kinetic energy.
9) A block, whose weight is 200 N, is pulled up a slope at a constant speed by means of a constant force of 150 N, as shown in figure:
b) by how much has the potential energy of B increased?
c) Account for the difference.
10) a) What is the kinetic energy of a car of 750 kg moving at 50 kmph ?
b) How much work must be done on the car to slow it from 100 kmph to 50kmph?
c) how much work must be done on the car to bring it rest?
d) the force that does the work showing the car is constant. Find the ratio of distance needed to show the car from 100 kmph to 500 kmph to the distance needed to slow it from 50 kmph to rest. State your conclusion in a sentence..
11) A burner consumes 110 kJ of energy in 55s. What is the power of the burner in kW ?
12) a body P has kinetic energy E. Another body Q, whose mass is 9 times that of the body P, also kinetic energy E. Calculate the ratio of the velocity of P and Q.
13) A body of mass 20 kg is moving with the velocity of 1 m/s, another body B mass 1 kg is moving with a velocity of 20m/s. Find the ratio of kinetic energy of A and B.
14) A bag of wheat weighs 200 kg. To what height should it be raised to so that its potential energy may be 9800 joules? g= 9.8m/s²
15) a body mass 60 kg has the momentum 3000 kg m/s. Calculate the kinetic energy and speed of the body.
16) A bullet of mass 0.05 kg strikes a wooden target 0.2m thick, with a velocity of 300m/s, and emerges out with a velocity of 100 m/s. Calculate
a) the loss in KE
b) the average force of friction of wood.
17) A truck weighing 1000 kg changes its speed from 36 kmph to 72 kmph in 2 minutes. Find the work done by the engine and its power.
18) A horse and dog are running with the same speed. What is the ratio of their kinetic energies if the mass of the horse is 10 times that of the dog ?
19) A cyclist along with the machines weighs 80 kg. Starting from rest , he picks up a velocity of 15m/s over a distance of 30m. Calculate
a) the work done by the cyclist.
b) the power developed by the cyclist in 4 seconds.
20) The work done by the heart for each beat is 1 joule . Calculate the power of the heart if it beats 72 times in a minute.
21) What is the power of a pump which takes 10 seconds to lift 100 kg of water to a water tank situated at a height of 20 m ? take g= 10m/a.
22) A man of mass of 6 kg runs up a flight of 30 steps in 15 seconds . If each step is 20cm high, calculate the power developed by the man. g= 10m/s²
23) a block of mass 30 kg is pulled up a slope with a constant speed by applying a force of 200 N parallel to the slope. A and B are initial and final position of the block.
b) calculate the potential energy by the block.
24) a) How fast should a man 60 kg runs so that his kinetic energyis 750 J?
b) a body of mass 1 kgs thrown vertically up with an initial speed of 5 m/s. What is the magnitude and direction of the force due to gravity acting on the body when it is at its highest point ?
25) A bullet of mass 50g is moving with a velocity of 500 m/s, it penetrates 10cm into a still target and comes to rest .
a) calculate the kinetic energy possessed by the bullet.
b) the average retarding force offered by the target.
26) A body of mass 1 kg falls from a height of 5 m. How much energy does it possess at any instant ? take g= 9.8 m/s² ?
27) An engine can pump 30,000 litres of water to a vertical height of 45m in 10 minutes. Calculate the work done by the machine and its power. g= 9.8 m/s²
(density of the water =103 kg/m³, 1000 litre = 1m³)
28) A machine raises a load of 750 N through a height of 16m in 5 seconds . Calculate the power at which the machine works .
29) If the power of a motor is 40 kW, at what speed can it raise a load of 20000 N ?
30) Two balls of mass ratio 1:2 are dropped from the same height.
a) State the ratio between their velocity when they strike the ground.
b) The ratio of the forces acting on them during motion.
31) A ball of mass 0.20 kg is thrown vertically upwards with an initial velocity of 20m/s. Calculate the maximum potential energy it gains as it goes up.
32) The work done by the heart is 1 joule per beat. Calculate the power of the heart if it beats 72 times in 1 minute.
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