A 100 N net force acts on a loaded dolly for 0.5 s. You have seen the two things that set how much momentum a force delivers: how big the force is, and how long it acts.
One quantity measures the two together. What is it?
You have seen that a larger net force causes a larger momentum gain, and that a longer acting time does too.
Here is the dolly again: a 100 N net force, acting for 0.5 s. One number should measure the whole delivery.
Multiply the force by the time: 100 × 0.5 = 50. That single number counts both.
One equation says that move for every force.
impulse = net force × time the force acts
In symbols: J = FΔt.
The product FΔt measures the total push the object receives over the whole time the force acts. This product is called the impulse.
With force in newtons and time in seconds, the dolly's impulse is written 50 N·s.
A 20 N net force acts on a cart for 4.0 s. Enter the impulse delivered to the cart in N·s.
A larger force means a larger impulse. A longer time means a larger impulse.
Bastian says: 'A 50 N net force acting on a cart for 2 s delivers a larger impulse than the same force acting for 1 s.' Is Bastian correct?
Impulse's symbol is a capital J. Later in the course, J will also abbreviate the joule, the energy unit, so an impulse value always carries its unit, N·s, and where the two could meet this course writes the word joule out in full.
A 40 N net force acts on a wagon for 3.0 s. State the impulse delivered.
Write down the values:
F = 40 N, Δt = 3.0 s, J = ?
Write down the equation:
J = FΔt
Substitute in the values, and calculate:
J = 40 × 3.0 = 120
The impulse is 120 N·s.
The same 40 N net force acts for only 1.5 s. State the impulse now.
Write down the values:
F = 40 N, Δt = 1.5 s, J = ?
Write down the equation:
J = FΔt
Substitute in the values, and calculate:
J = 40 × 1.5 = 60
The impulse is 60 N·s. Half the time, half the impulse.
A 45 N net force acts on a sled for 0.6 s. Enter the impulse delivered to the sled in N·s.
Which statement says what the impulse on an object is?
A 15 N net force acts on a cart for 6.0 s. A 45 N net force acts on an identical cart for 2.0 s. Which statement is correct?
The net force on an object multiplied by the time the force acts has its own name. What is this product called?