The force required to hold a water hose

Calculate the force required to hold a water hose of radius 0.04 m when it emits a jet of water at a speed of 20 m/s.

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Object, String & Elevator

An object of mass m is hanging by a string from the ceiling of an elevator. The elevator is moving upward, but slowing down.

What is the tension in the string?


a) zero
b) greater than mg
c) exactly mg
d) less than mg

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If the solar system were reduced

Solar System (artist's impression) If all the linear dimensions of the solar system were reduced in some proportion, then what will be the length of Earth’s year?


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A hockey player & referee

hockeyA 100 kg hockey player pushes a 80 kg referee with a force of 800N. Assuming they on a frictionless ice surface and the push lasts for 0.5 seconds, find the following: a) the acceleration experienced by each person b) the maximum velocity reached by each person c) do the resulting motions depend on which person instigated the pushing?   Continue reading

Newton’s Second Law Question 2


An object has a weight of 5.10 newtons (N) at the level of the sea, where the acceleration due to gravity is 9.81 m/s^2.

What is the acceleration caused by gravity on the object if it is placed in a spaceship to 1,000 km above the sea level, where the gravity exerts a force of 3.81 N on the object?


F=m*a   So, let’s calculate a mass of the object.

Now, we could calculate acceleration where the gravity exerts a force of 3.81 N on the object.

m=F/a=5.10/9.81=0.52 kg

a=F/m=3.81/0.52=7.33 m/s^2


Newton’s Second Law Question 1

The car changed a speed from 5 m/s to 10 m/s for 10 sec. The approximate mass of the car 1500 kg. Please calculate a total force.


a=(V-V0)/t=(10-5)/10=0.5 m/s^2

F=m*a=1500*0.5=750 N