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physics Advanced Subsidiary (AS) Level Physics.
 
Solved problems for the chapter:
 

Newton's First Law of Motion

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Detailed solution steps are available at:
 
https://en.openprof.com/wb/chapter:newton_s_first_law_of_motion/5078/


Example 1.

An elevator with a mass of starts to rise with an acceleration of . What is the force in the elevator rope? What will be the force in the rope if the elevator descends with the same acceleration?

    
Example 2.

Two bodies are suspended via a rope on an attached pulley. The first body has a mass of 0.1 kg and the second 0.3 kg. The bodies are first held with the hand and then released. With what acceleration are they moving? What is the force on both sides of the rope?

    
3.

A rocket model with a mass of is launched vertically upwards with an initial velocity of . It reaches its maximum height in . With what average force does air resistance impede the rocket?

    
4.

Kelvin keeps a barrel on an inclined plane so that it doesn't roll down. The angle of the slope is and the weight of the barrel is 80 kg. With what force does Kelvin hold on to the barrel?


    
5.

A log weighing 50 kg is dragged on a horizontal surface. The frictional force between the log and the surface is 200 N. What force must be applied on the log for the acceleration to be ?

    
6.

  • Two masses of 0.5 kg each are suspended on the rope of an attached pulley - each on its own side (Figure A). Are the masses at rest? What is the force of the rope?


  • We hang an additional weight with a mass of 0.1 kg on the left side (picture B). In which direction is the weight moving? What is the acceleration of the motion?

    
7.

Determine whether the description of Newton's first or third laws applies in the given cases.


  • A car drives uniformly on a level road. It is acted upon by the force of the engine and, conversely, by the same force of air resistance.

  • The force of water resistance inhibits the navigation of the ship, and the ship acts with force on the water to cause waves. Both forces are equal and opposite.

  • Push a trolley on a flat surface with the force of your hands so that it moves uniformly.

  • A locomotive acts with force F on the train carriages and accelerates them. The wagons operate with the same opposite force on the locomotive.

  • A body hangs on a string. The sum of the force on the string and the weight of the body is zero, so the body is at rest.

  • A body hangs on a string. With its weight it acts on the string vertically downwards, and the string with the equal and opposite force on the body.

    
8.

Identify which of the listed motions below is described by Newton's first law. Justify the answer.

  • Brock meandering evenly along the snowy slope.

  • Raindrops falling from the sky at a speed of 8 m/s.

  • Children on the carousel rotating at a constant speed.

  • A passenger plane flying on a straight track and at a constant speed over the Atlantic.

  • A stone falling to the ground from a height of 10 m.

    

9.

Tom pulls a log with a force of 30 N at an angle of 45 ° with respect to the horizontal. The frictional force between the log and the ground is 21 N, the weight of the log is 40 N, and the ground acts with a force of 19 N on the log. Draw all the forces acting on the log on a scale and determine whether Newton's first law applies to the motion of the log.


    
10.

A car is driven on a flat road. The force of the engine is constantly opposed by the force of air resistance, which depends on the speed of the vehicle. Consider four cases:

  • The engine force is equal to the resistance force. The magnitude of each is 0 N.

  • The engine force is 800 N and the resistance force is 200 N.

  • The engine force is equal to the resistance force. The magnitude of each is 400 N.

  • The engine force is 200 N and the resistance force is 400 N.

Which of the cases does Newton's first law describe?

    
11.

A square-shaped log is dragged across a table so that it moves uniformly and on a straight line. If the applied force is 4 N and the weight of the log is 6 N, draw to scale, all the forces acting on the log.

    
12.

The mass of a rocket filled with fuel is 380 tonnes. The rocket engines develop a thrust of 4.6 MN. Calculate the resultant of the forces acting on the rocket after take-off.

    
13.

Joseph holds a bucket of mortar tied to a rope so that the bucket rests. The rope is passed over a pulley attached to the top of the masonry scaffold, as shown in the figure. On Joseph's side, he pulls the rope at an angle of to the vertical. The weight of the bucket with mortar is 20 kg. How much force does Joseph apply on the rope? Does the magnitude of the force depend on the angle at which Joseph pulls the rope?


    
14.

Victor wants to lift a block of mass 120 kg using a pulley. The pulley has a fixed part with two wheels and a moving part with one wheel. A tow rope is passed through all three wheels, as shown in the figure. He hangs the load on the moving part of the pulley. What force does Victor apply on the free part of the rope to keep the load in the air at rest? The moving part of the pulley has a negligible mass.


    
15.

A crate of mass 80 kg rests strapped to the rope of a fixed and movable pulley as shown in the figure. With how much force does Vincet have to pull the rope to keep the crate stationary in the air?


    
16.

A load of mass 40 kg rests a smooth inclined plane of angle to the horizontal. The block is attached to an unknown weight with a rope over a pulley so that it does not slip down the slope - see picture. What is the mass of the unknown weight?


    
17.

Snowflakes fall uniformly at a speed of 2 m/s. The weight of a snowflake is 0.1 g. What forces act on a snowflake and what is their size?


    
18.

Which statement about Newton’s laws of motion is correct?


  • The first law follows from the second law.


  • The third law follows from the second law.


  • Conservation of energy is a consequence of the third law.


  • Conservation of linear momentum is a consequence of the first law.