What is one newton?

The idea

One newton is the force that produces an acceleration of 1 m s–2 on an object of mass 1 kg, so 1 N = 1 kg m s–2.

A name for a unit

Force is mass times acceleration. Mass is in kilograms and acceleration in metres per second per second.

What do you think a force of one newton does to a mass of one kilogram?

• Gives it an acceleration of one m s⁻²
• Gives it a speed of ten m s⁻¹
• Makes its mass zero

Build a newton

Choose the mass and the acceleration and read the force.

A force from mass and acceleration

With 1 kg and 1 m s⁻² the product is 1 kg m s⁻², and this is what we call one newton. With 4 kg and 3 m s⁻² the force needed is 12 N.

One newton is the force that produces an acceleration of 1 m s⁻² on an object of mass 1 kg, so 1 N = 1 kg m s⁻².

Notes

1 newton = the force that gives 1 kg an acceleration of 1 m s⁻²: 1 N = 1 kg m s⁻².

Check yourself

One newton is the force that…

Which is equal to one newton?

What force gives an object of mass 4 kg an acceleration of 3 m s⁻²?

Answer: 12 N

F = ma = 4 kg × 3 m s⁻² = 12 N.

If you hold a 100 g mass in your palm, the upward force your palm applies on it is around…

• produces an acceleration of 1 m s⁻² on an object of mass 1 kg — correct. Yes!
• produces an acceleration of 1 m s⁻² on an object of mass 10 kg. On 10 kg a force of 1 N gives an acceleration of only 0.1 m s⁻².
• produces a speed of 1 m s⁻¹ on an object of mass 1 kg. The newton is defined through acceleration, not speed.
• 1 kg m s⁻¹. That is a mass multiplied by a speed. A force is a mass multiplied by an acceleration.
• 1 kg m s⁻² — correct. Yes!
• 1 kg s⁻². This leaves out the metre. A force is mass × acceleration, which is kg m s⁻².
• 100 N. 100 N would be 100 times larger than the force of holding a 100 g mass.
• 0.01 N. 0.01 N would be 100 times smaller than the force needed to hold a 100 g mass.
• 1 N — correct. Yes!