The portal has been deactivated. Please contact your portal admin.

Lesson Worksheet: Newton’s Third Law of Motion Mathematics

In this worksheet, we will practice solving problems on Newton’s third law.

Q1:

An elevator is moving vertically upward at a constant speed. A man of mass 150 kg is standing inside. Determine the reaction force of the floor on the man. Take 𝑔=9.8/ms.

Q2:

Fill in the blank with <, >, =, , or : When a body of mass 𝑚 is suspended from a spring scale fixed at the ceiling of an elevator and the elevator descends with uniform acceleration, then the apparent weight the real weight.

  • A<
  • B
  • C=
  • D
  • E>

Q3:

An elevator is accelerating vertically upward at 2.6 m/s2. A man of mass 124 kg is standing inside. Determine the reaction force of the floor on the man.

Q4:

An elevator was accelerating vertically downward at 1.7 m/s2. Given that the acceleration due to gravity is 𝑔=9.8/ms, find the reaction force of the floor to a passenger of mass 103 kg.

Q5:

A body of mass 45 kg was placed in a spring balance fixed to the ceiling of an elevator. If the elevator was accelerating downward at 105 cm/s2, what would the apparent weight of the body be? Consider the acceleration due to gravity to be 9.8 m/s2 and round your answer to two decimal places.

Q6:

A body of mass 75 kg was attached to a string fixed to the ceiling of an elevator. Starting from rest, the elevator began accelerating vertically upward at 44 cm/s2. During this time the tension in the string was 𝑇. After accelerating, the elevator continued moving at the speed it had gained, at which point the tension in the string was 𝑇. Finally, the elevator decelerated at 24 cm/s2, at which point the tension in the string was 𝑇. Determine the magnitudes of 𝑇, 𝑇, and 𝑇. Consider the acceleration due to gravity to be 9.8 m/s2.

  • A𝑇=717N, 𝑇=735N, 𝑇=768N
  • B𝑇=73N, 𝑇=75N, 𝑇=78N
  • C𝑇=768N, 𝑇=735N, 𝑇=717N
  • D𝑇=78N, 𝑇=75N, 𝑇=73N

Q7:

A lift is ascending with an acceleration of 140 cm/s2. Given that a person standing inside the lift is exerting a force of 88 kg-wt on the floor, find his mass. Take 𝑔=9.8/ms.

Q8:

A body of mass 4 kg is hanging from a spring balance fixed to the ceiling of a lift. Given that the reading on the balance is 1‎ ‎042 g-wt, determine the magnitude of the acceleration of the lift to the nearest two decimal places. Take 𝑔=9.8/ms.

Q9:

A man was standing on a set of scales in an elevator, recording the readings as the elevator moved. His first reading was when the elevator was accelerating upward at a rate of 7𝑎. He made another reading when the elevator was accelerating downward at a rate of 8𝑎. Given that the ratio between the two readings was 41:, determine 𝑎𝑔: where 𝑔 is the acceleration due to gravity.

  • A112:
  • B121:
  • C113:
  • D131:

Q10:

A body of mass 686 g was suspended to a spring balance fixed to the ceiling of a lift. When the lift started moving, the reading on the balance was 672 g. Determine whether the lift was ascending or descending, and find the speed 𝑣, 5 seconds after it started moving. Consider the acceleration due to gravity 𝑔=9.8/ms.

  • Aascending, 𝑣=1/ms
  • Bascending, 𝑣=0.51/ms
  • Cdescending, 𝑣=1/ms
  • Ddescending, 𝑣=0.51/ms

This lesson includes 40 additional questions and 216 additional question variations for subscribers.

Nagwa uses cookies to ensure you get the best experience on our website. Learn more about our Privacy Policy.