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physics Physics For High Schools (KS4)
 
Solved problems for the chapter:
 

Resultant by Calculation

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Detailed solution steps are available at:
 
https://en.openprof.com/wb/chapter:resultant_by_calculation/5058/


Example 1.

Determine whether or not, each of the following statements is correct:


  • An apple is hanging on a branch of a tree. The resultant of the forces acting on the apple is equal to the weight of the apple.


  • A car is standing in front of a traffic light. The sum of all the forces acting on the car is zero.


  • A car moves evenly on a level road. The resultant of all the forces acting on the car is equal to the force of the engine.


  • We hang a 4 N weight on a spring balance which is attached to a retort stand. It stretches by 2 cm. In the end, the resultant of the forces acting on the weight is zero.


  • There is a package on a table. Because it is at rest, no force acts on it.


    
Example 2.

A boat, tied to a rope, is towed on the water at a speed of 2 m/s. The traction force is 600 N. With what force does the boat resist the flow of the water?


    
3.

A ball rolls uniformly and in a straight line on a flat surface at a speed of 2 m/s - Figure A. At some point, two equal but oppositely directed forces of magnitude 3 N each begin to act on the ball - Figure B. How will the ball move after the forces start to act?


    
4.

A skier of weight 600 N steps on soft snow. The moment he steps on the snow, the force of the ground is 400 N.

  • What is the resultant force and in which direction does it act?

  • What force needs to change and by how much for the skier to rest?


    
5.

Seven friends compete in a tug of war. A group of four friends pulls the rope to the right while the other three pull to the left - see picture. The right group pulls with forces of 20 N, 80 N, 40 N, and 60 N, and the left with forces of 60 N, 80 N, and 80 N. Which group acts with greater force on the rope and by how much?


Pulling a rope. The forces are not drawn to scale!

    
6.

The resultant of all forces acting on a box must be greater than 300 N for the box to move. Forces of 600 N to the right and 800 N to the left act on the box, as shown in the figure. Will the box move?


The forces on the box are not drawn to scale .

    
7.

A table weighing 200 N stands on four legs. How much force does each foot exert on the ground?


    
8.

John wants to use a fixed pulley to lift a load weighing 800 N. His mass is 60 kg. Will he succeed?


    

9.

Nick and Sam each hold two attached springs on their sides and pull them as shown in the picture. Nick acts on the left spring balance with a force of 8 N. How much force do the left and right spring balances show? What do they show if Sam reduces the force to 6 N?


    
10.

A spring balance attached to a stand has a weight of 0.5 N hung on it. Another similar spring balance, attached below the weight, also has another 0.5 N weight hung on it - see the figure below. Each spring balance weighs 0.3 N. How much force do both spring scales show?


    
11.

Which moving object has a resultant force acting on it?


  • a diver rising vertically through water at constant speed


  • an aircraft circling an airport at constant speed


  • a train going up a straight incline at constant speed


  • a parachutist descending vertically at terminal velocity


    
12.

A car engine causes a forward force of to act on the car. The total resistive force on the car is . What is the resultant force on the car?









    
13.

A sledge is pulled in a straight line by dogs, as shown.




The dogs produce a total horizontal driving force of . The frictional force between the sledge and the surface is and the air resistance on the sledge is . What is the resultant force acting on the sledge?









    
14.

Four objects are moving. Which object has a zero resultant force acting on it?


  • the object moving at a decreasing speed


  • the object moving at an increasing speed


  • the object moving at a constant speed in a circle


  • the object moving at a constant speed in a straight line

    
15.

On the diagram shown, what is the magnitude of the resultant force of the two vectors?











    
16.

The diagram shows two forces acting at right angles to each other.




What is the resultant of the two forces?









    
17.

A cart experiences a forward force of . The cart also experiences a backward force of . There are no other forward or backward forces on the cart. What is the resultant force on the cart?


  • backwards


  • forwards


  • backwards


  • forwards

    
18.

A stone of mass is fired from a catapult. The velocity of the stone changes from 0 to in . What is the average resultant force acting on the stone while it is being fired?









    

19.

An object decelerates from to in a time of . It has a mass of . What is the resultant force on the object?









    
20.

A ship sails due North at a speed of . A current in the water begins to move from East to West. The speed of this current is . What is the magnitude of the resultant velocity of the ship?









    
21.

A car has a mass of . A constant resultant force acts on the car and the car accelerates from to in . What is the magnitude of the resultant force acting on the car?









    
22.

A train travels at a constant speed along a straight track. Which statement about the resultant force on the train is correct?


  • It is bigger than the thrust of the engine.


  • It is constantly increasing.


  • It is equal to the thrust of the engine.


  • It is zero.

    
23.

A satellite orbits the Earth at constant speed in a circular orbit. Which statement is correct?


  • The resultant force on the satellite is zero.


  • The resultant force on the satellite is towards the Earth.


  • The resultant force on the satellite is away from the Earth.


  • The resultant force on the satellite is in the direction of its motion.