ques 1.......a boy walks from his home to his school at an average speed of 10 km per hour and returns to his home at an average speed of 15 km per hour . what is his average speed in km per hour during the entire round trip ?
ques 2........a thief running at a speed of 8 km per hour is chased by a police man whose speed is 10 km per hour if the thief is 100 metre ahead of the policemen what is the time required by the police men to catch the thief ?
ques 3....a man of mass 60 kg jumps at a speed of 4 meters per second from a stationary boat and as a result the boat moves off with a speed of 0.8 meters per second. what is the mass of the boat?
ques 4.....two persons start walking at a speed of 3 km per hour from a road intersection along two road that make an angle of 60 degree with each other . what will be the shortest distance separating them at the end of 20 minutes?
ques 5....a car starts at rest and moves on a straight road with a uniform acceleration of 10 m/s square for the first 10 seconds . during the next 10 seconds , the car moves with the velocity it has attained . what is the total distance covered by car in 20 seconds ?
ques 6....a crane can raise a load of mass 120kg vertically upward with a speed of 5 metres per second . if the acceleration due to gravity is 10 m/s square what is the power ( in kilowatts ) of the engine ?
ques 7.....water in a river is flowing from west to east at a speed of 5 metres per minute. a man on the south bank of the river , capable of swimming at a speed of 10 mete per minute , wishes to cross the river in the shortest possible time . in which direction must be swim ?
ques 8....a string can withstand a maximum tension of 25N . what is the greatest speed at which a body of mass 1kg can be whriled in a horizontal circle using 1 metre length of the string?
ques 9.....the escape velocity for a body projected vertically upwards from the surface of the earth is ve . if the body is projected in a direction making at angle of 30 degree with the vertical, what is the escape velocity ?
ques 10....the work done in a raising a body of mass 2kg to a height of 1 metre above the ground is ? (
the accelration due to gravity is to m/s square.
ques 11 ...a sound generator placed under water has a frequency of 580 hz. it produces waves of wavelength 2.5 m. what is the speed of sound in water ?
ques 12 ...a man standing in front of a high wall fires a gun. he hears the echo 2 seconds after the gun is fired . if the speed of sound is 340m/s . how far is the wall from the man. ?
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answers
1 ----12
2----- 3min
3 --------300kg
4-----1km
5-----1500m
6-----6kilowatt
7---5m/s
8---11.2km/s
9-----20 joule
10--------1450m/s
11------340m
1. average speed=distance/time
assume d is the one way distance, so 2d will be the total distance.
time1..going one way= distance/15km/hr
time2..other way=distance/10km/hr
avgspeed=2d/(time1+time2)
= 2d/(d/10 + d/15)=2*150/25 work that out=12km/hr
I will happily critique your work or thinking on the others.
did anyone one has gut to solve all these ques. cuz i don hav guts
Sure! I'll provide you with step-by-step explanations for each of the questions.
Question 1:
To find the average speed, we need to calculate the total distance traveled and the total time taken.
Let's assume the distance between the boy's home and school is D km.
The time taken to go from home to school = D/10 hours.
The time taken to return from school to home = D/15 hours.
The total time taken for the round trip = (D/10) + (D/15) hours.
To find the average speed, we divide the total distance by the total time:
Average speed = (2D) / [(D/10) + (D/15)]
Simplifying the expression, we get: Average speed = (2D) / [(3D + 2D)/30]
Average speed = (2D) / [(5D/30)]
Average speed = 60/5
Average speed = 12 km/hr
Therefore, the average speed during the entire round trip is 12 km/hr.
Question 2:
To find the time required by the policeman to catch the thief, we need to find the relative speed between them and then divide the distance between them by the relative speed.
The relative speed between the thief and policeman = 10 km/hr - 8 km/hr = 2 km/hr.
Distance between them = 100 meters = 0.1 km.
Time = Distance / Speed
Time = 0.1 km / 2 km/hr
Time = 0.05 hours
Converting hours to minutes: 0.05 * 60 = 3 minutes
Therefore, the time required by the policeman to catch the thief is 3 minutes.
Question 3:
To find the mass of the boat, we can use the law of conservation of momentum. The momentum before the jump is equal to the momentum after the jump.
Mass of the man = 60 kg
Speed of the man = 4 m/s
Mass of the boat =?
Momentum before = Momentum after
(mass of the man) * (initial speed of the man) = (mass of the man + mass of the boat) * (final speed of the boat)
(60 kg) * (4 m/s) = (60 kg + mass of the boat) * (0.8 m/s)
240 kg⋅m/s = (60 kg + mass of the boat) * (0.8 m/s)
Simplifying the equation, we have:
60 + mass of the boat = 300
Mass of the boat = 300 - 60
Mass of the boat = 240 kg
Therefore, the mass of the boat is 240 kg.
Question 4:
To find the shortest distance separating the two persons at the end of 20 minutes, we need to find the vector sum of their displacements along both roads.
Speed of each person = 3 km/hr
Time = 20 minutes = 20/60 hours = 1/3 hours
Distance covered by each person = (Speed * Time)
Distance covered by each person = (3 km/hr) * (1/3 hours)
Distance covered by each person = 1 km
Using the law of cosines, the shortest distance between them is:
Shortest distance = √(Distance^2 + Distance^2 - 2 * Distance * Distance * cos(60°))
Shortest distance = √(1^2 + 1^2 - 2 * 1 * 1 * cos(60°))
Shortest distance = √(2 + 2 - 2 * cos(60°))
Shortest distance = √(4 - 2 * cos(60°))
Shortest distance = √(4 - 2 * 0.5)
Shortest distance = √(4 - 1)
Shortest distance = √3
Shortest distance ≈ 1.732 km
Therefore, the shortest distance separating them at the end of 20 minutes is approximately 1.732 km.
I'll continue with the explanations for the remaining questions in the next response.