# Forces

Question 3

What force is required to give mass m = 40 kg acceleration a = 2 m/c2 ?

Answer

60 N

80 N

40 N

20 N

Question 4

What force is required to keep mass m = 20 kg

moving with a constant speed along straight line?

Answer

100 N

80 N

60 N

No force required

Question 5

Two boxes have the same size, but one box is empty and the other has books inside.

The same force is applied to each box. What box will have the bigger acceleration?

Answer

Empty box

Box with books

Boxes will have the same acceleration

Impossible to make a conclussion

Question 6

According to the Second Newton's Law,

if you drop the ball it will fall down with acceleration

(because of gravity force).

Gravity on a Moon is less than on Earth.

If you drop the same ball on the Earth and on the Moon

Answer

acceleration on the Earth will be bigger than on the Moon

acceleration on the Earth will be less than on the Moon

acceleration will be the same on the Earth and on the Moon

ball will not fall down on the Moon

Question 8

Gravity force applied to the monitor is 50 N.

Monitor is on a horizontal surface of table and doesn't move.

What is the magnitude and direction of surface reaction?

Answer

50 N directed horizontally

50 N directed down

50 N directed up

There is no surface reaction because monitor doesn't move

Question 9

Imagine a book on the horizontal surface. without motion (at rest).

Gravity force pushing the book down with force 10 N,

but the book is remaining on the surface without motion (at rest).

What is the Net Force applying to the box?

Answer

The Net Force is 10 N and directed up

The Net Force is 10 N and directed down

The Net Force is 20 N

The Net Force is zero

Question 10

Following two forces applying to the object:

one 30 N to the right (------------------->)

another 10 N to the left (<-----)

What is the Net Force?

Answer

-----> 10 N

----------> 20 N

---------------> 30 N

10 N <-----

#### Solution Summary

This solution explains how to solve several problems dealing with forces.