Weight Examples in Physics

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Weight.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Physics.

Concept Recap

The gravitational force acting on an object due to its mass, directed toward the center of a massive body.

How hard gravity pulls you toward the ground — it changes on different planets.

Read the full concept explanation →

How to Use These Examples

Read the first worked example with the solution open so the structure is clear.
Try the practice problems before revealing each solution.
Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Weight asks students to choose the object, list external interactions, and reason from the resulting force or torque pattern.

Common stuck point: Students often know a formula related to weight but skip the recognition step: Have I isolated one system and listed the external forces or torques acting on it before applying a law? That leads to a correct-looking substitution attached to the wrong physical model.

Sense of Study hint: Ask: Have I isolated one system and listed the external forces or torques acting on it before applying a law?

Worked Examples

Example 1

easy

What is the weight of a

12 \text{ kg}

object on Earth? Use

g = 9.8 \text{ m/s}^2

Answer

W = 117.6 \text{ N}

First step

Use the weight formula:

W = mg

, where

m

is mass and

g = 9.8 \text{ m/s}^2

Full solution

2
Identify the given values: $m = 12 \text{ kg}$ , $g = 9.8 \text{ m/s}^2$ .
3
Substitute and calculate: $W = 12 \times 9.8 = 117.6 \text{ N}$

Weight is the gravitational force acting on an object, calculated as the product of mass and gravitational acceleration. It is measured in newtons.

Example 2

hard

A person weighs

686 \text{ N}

on Earth (

g = 9.8 \text{ m/s}^2

). What would they weigh on Jupiter where

g_J = 24.8 \text{ m/s}^2

Example 3

medium

A box has mass

25 \text{ kg}

. (a) What is its weight on Earth (

g = 9.8 \text{ m/s}^2

)? (b) What is its weight on Mars (

g_M = 3.71 \text{ m/s}^2

Example 4

medium

70 \text{ kg}

astronaut stands on a planet where her weight reads

560 \text{ N}

. What is the gravitational acceleration on that planet?

Example 5

medium

On Earth's surface (

g = 9.8 \text{ m/s}^2

) a person weighs

784 \text{ N}

. On a different planet they weigh

200 \text{ N}

. What is

g

on that planet?

Example 6

medium

A scale reads

W

for a stationary

40 \text{ kg}

box. The same box, placed in an elevator accelerating upward at

2 \text{ m/s}^2

, reads

W'

. Compute both. Use

g = 9.8 \text{ m/s}^2

Example 7

hard

60 \text{ kg}

person stands in an elevator. The scale reads

480 \text{ N}

. What is the elevator's acceleration? Take upward as positive. Use

g = 9.8 \text{ m/s}^2

Example 8

hard

Using Newton's law of universal gravitation, find the weight of a

1.0 \text{ kg}

mass at Earth's surface. Earth mass

M = 5.97 \times 10^{24} \text{ kg}

, radius

R = 6.37 \times 10^6 \text{ m}

G = 6.67 \times 10^{-11} \text{ N·m}^2/\text{kg}^2

Example 9

hard

Astronauts in the International Space Station experience apparent weightlessness despite Earth's gravity pulling them. Explain in one short paragraph why their apparent weight is approximately zero.

Example 10

hard

1500 \text{ kg}

car drives over a hump in the road shaped like the top of a circle of radius

50 \text{ m}

at speed

10 \text{ m/s}

. What is the apparent weight (the normal force from the road) at the top? Use

g = 9.8 \text{ m/s}^2

Example 11

challenge

Compute the gravitational acceleration at the Moon's surface from Newton's law. Moon mass

M_M = 7.35 \times 10^{22} \text{ kg}

, radius

R_M = 1.74 \times 10^6 \text{ m}

G = 6.67 \times 10^{-11} \text{ N·m}^2/\text{kg}^2

Example 12

easy

A scale at the equator reads slightly less than a scale at the North Pole for the same mass. Why?

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

medium

An object weighs

196 \text{ N}

on Earth. What is its mass? Use

g = 9.8 \text{ m/s}^2

Example 2

easy

15 \text{ kg}

backpack is on Mars where

g = 3.7 \text{ m/s}^2

. What is its weight?

Example 3

easy

5\text{ kg}

object sits on Earth (

g=9.8\text{ m/s}^2

). Find its weight.

Example 4

easy

What is the SI unit of weight?

Example 5

easy

10\text{ kg}

object is on the Moon,

g=1.6\text{ m/s}^2

. Find its weight.

Example 6

easy

Does an object's weight change if it is moved to a planet with stronger gravity?

Example 7

easy

Using

g=10\text{ m/s}^2

, find the weight of a

3\text{ kg}

bag.

Example 8

easy

Is weight a vector or a scalar?

Example 9

easy

An object's weight is

60\text{ N}

on Earth (

g=10\text{ m/s}^2

). Find its mass.

Example 10

easy

Two objects have masses

2\text{ kg}

and

4\text{ kg}

on Earth. Which weighs more?

Example 11

medium

8\text{ kg}

object hangs from a spring scale at rest (

g=9.8

). What does the scale read in newtons?

Example 12

medium

A person weighs

588\text{ N}

on Earth (

g=9.8

). Find their weight on the Moon (

g=1.6

Example 13

medium

2\text{ kg}

object hangs from two cases: at rest, then accelerating up at

g=9.8

unchanged. What is its weight either way?

Example 14

medium

On planet X, a

5\text{ kg}

object weighs

60\text{ N}

. Find

g

on planet X.

Example 15

medium

1.5\text{ kg}

book sits on a table (

g=9.8

). What upward normal force does the table provide?

Example 16

medium

4\text{ kg}

mass and a

6\text{ kg}

mass are taped together on Earth (

g=10

). Find the total weight.

Example 17

challenge

70\text{ kg}

astronaut stands on a scale in a spacecraft accelerating upward at

4\text{ m/s}^2

far from gravity (

g\approx 0

). What does the scale read?

Example 18

challenge

An object weighs

100\text{ N}

at Earth's surface. At a height where

g

is one-quarter as strong, find its weight.

Example 19

challenge

50\text{ kg}

person rides an elevator accelerating downward at

2\text{ m/s}^2

(

g=9.8

). Find their apparent weight.

Example 20

medium

12\text{ kg}

object hangs at rest from a rope (

g=10

). Find the rope tension.

Example 21

medium

5\text{ kg}

object is weighed on Earth (

g=9.8

) and on Mars (

g=3.7

). Find both weights.

Example 22

medium

An object of weight

45\text{ N}

on Earth (

g=9

) is taken to a planet where it weighs

30\text{ N}

. Find that planet's

g

Example 23

easy

A bag of flour has mass

5 \text{ kg}

. What is its weight on Earth? Use

g = 9.8 \text{ m/s}^2

Example 24

easy

On the Moon,

g_M = 1.62 \text{ m/s}^2

. What is the weight of a

50 \text{ kg}

astronaut on the Moon?

Example 25

easy

An apple has mass

0.2 \text{ kg}

. What is its weight on Earth (

g = 9.8 \text{ m/s}^2

Example 26

medium

An object weighs

98 \text{ N}

on Earth and

16 \text{ N}

on the Moon. What is the gravitational acceleration on the Moon? Use

g_E = 9.8 \text{ m/s}^2

Example 27

medium

3 \text{ kg}

block hangs from a vertical spring scale at rest. What does the scale read? Use

g = 9.8 \text{ m/s}^2

Example 28

medium

Two identical bricks each have mass

2 \text{ kg}

. What is their combined weight on Earth (

g = 9.8 \text{ m/s}^2

Example 29

medium

An astronaut and her spacesuit together have total weight

980 \text{ N}

on Earth (

g = 9.8 \text{ m/s}^2

). What is the total mass?

Example 30

medium

A bag of sugar reads

4.9 \text{ N}

on an Earth scale (

g = 9.8 \text{ m/s}^2

). How many grams of sugar is that?

Example 31

hard

A box of mass

20 \text{ kg}

is being lifted by a rope at constant velocity. What is the tension in the rope? Use

g = 9.8 \text{ m/s}^2

Example 32

hard

At what altitude above Earth's surface does an object's weight drop to half its surface value? Earth radius

R = 6.37 \times 10^6 \text{ m}

Example 33

hard

Jupiter has roughly

g_J = 24.8 \text{ m/s}^2

at its cloud tops. A package weighs

588 \text{ N}

on Earth (

g = 9.8 \text{ m/s}^2

). How heavy would the same package feel on Jupiter?

Example 34

challenge

0.50 \text{ kg}

rock hangs from a spring scale inside an elevator. The scale reads

3.0 \text{ N}

. Is the elevator accelerating up or down, and at what magnitude? Use

g = 9.8 \text{ m/s}^2

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Related Concepts

Mass Force Free Fall Gravity Normal Force

Background Knowledge

These ideas may be useful before you work through the harder examples.

massforcefree fall