Lesson video

Hi, I'm Miss Mia.

Thank you so much for joining me in this lesson.

I'm super excited, let's get started.

In this lesson, you'll be able to identify levers and describe their purpose and how they work.

Your keywords are on the screen now.

You can write them down if you'd like to.

So we've got lever, pivot, effort, load, force multiplier.

Great, let's find out what these keywords mean.

A lever is a simple machine designed to use the turning effect of a force.

A lever will rotate around a pivot.

The force applied to a lever is called the effort.

The force produced by a lever is called the load.

If a lever produces a larger load force than the effort force, it is a force multiplier.

So this lesson is all about levers.

We've got three lesson cycles today and our first lesson cycle is to do with turning effects.

We're then gonna be identifying levers.

And lastly, we'll be looking at predicting the size of turning effects.

Let's get started.

Forces can, one, change the motion of an object by speeding it up or slowing it down.

Changing the direction of movement.

Two, forces can change the shape of an object either by squashing or stretching it.

And three, make an object rotate.

Forces can have a turning effect on objects.

For example, to open a door, you can pull or push on any point.

The force causes the door to rotate around its hinges.

To make a roundabout spin, you can push it.

The roundabout rotates around the center.

The handle on a door is placed on the opposite side to the hinges.

So you've got the hinges on the left and the handle on the right.

If the handle was near to the hinge, it would be harder to make the door turn when you pushed or pulled.

A smaller force is needed to cause the turn when the distance between the force and the turning point is larger.

Over to you, a classroom door is open, a pupil tries to close it.

Which statement is correct?

Is it A, more force is needed at point A?

B, more force is needed at point B?

Or C, the same amount of force is needed at A and B?

What do you think?

You can pause the video here and click play once you've got the answer.

So what did you get?

If you got A, you are correct.

More force is needed at point A to try and close it.

Doors are held shut by latches, which slide into a doorframe.

To move the latch, a handle is rotated around a spindle.

The handle is long to increase the turning effect.

Back to you.

To open this door, the handle needs to be rotated downwards, anti-clockwise.

Which point shows where the largest force would be needed?

Is it A, B or C?

You can pause the video here and click play once you've got the answer.

So what did you get?

If applying the largest force at point A will easily open this door.

Onto our task.

So task A, the figure shows two jars with lids that twist off.

The lids are both as tight as each other.

Which jar will need the largest force to twist off?

Explain your answer.

You can pause the video here and click play once you've done that.

So what did you get?

So jar Y will take the greatest force.

The top to jar Y is smaller.

So you are putting the force closer to the point of rotation.

That means you will need a larger force to cause the rotation than for jar X where the force will be further from the center.

Well done if you got that correct.

Let's move on.

Lesson cycle two, identifying levers.

All levers have a point which they can rotate around.

This point is called the pivot.

The pivot could be a set of hinges.

For example, on a door.

An axle, for example, a door handle.

A simple point, for example a seesaw.

Levers also need a point where the force is applied.

The force applied to a lever is called the effort.

The effort can be a push or a pull.

To cause a turning effect the effort must act at a distance away from the pivot.

The effort on the lever will cause another force to act as the lever rotates.

This force is called the load.

The simplest lever looks like this.

So here we have a solid bar.

There's our pivot.

Here, we're going to apply some effort away from the pivot.

And then this results in the load.

There are three types of lever.

So here we have one example, pivot between effort and load.

Example two, load between effort and pivot.

And example three, effort between load and pivot.

So some levers are easy to spot.

They have a solid bar shape.

So in this example, a crowbar or pry-bar is a solid metal bar that rotates around a curved end that provides a pivot.

So here you can see that in action.

The pivot of the crowbar is between the effort and load.

The instructions on this can opener show it being used as a lever.

The joint acts as a pivot.

Pulling up on this end produces the effort.

This produces a downward force on this end.

Scissors act as a pair of connected levers.

Let's find out how.

So here we can see effort forces are used on the handles.

The blades rotate around the pin.

The effort acts on whatever the scissors are cutting.

Over to you.

A screwdriver is being used as a lever to open a can of paint.

I'd like you to match the labels correctly.

So we've got on the left, A, B, and C.

And then on the right we've got effort, load, pivot.

You can pause the video here and click play once you've matched the labels correctly.

So how did that go?

Well, A, you should have got as the load.

B is the pivot.

And then C, you should have got as effort because we can see here, see that force is being applied here.

Well done if you got that correct.

Let's move on.

Now, a wheelbarrow acts as a lever.

An effort force is used on the handles.

The wheelbarrow is not an obvious lever.

The load is between the effort and pivot.

The weight of the soil is the load.

The wheel acts as the pivot.

So this one can be a bit harder to spot sometimes.

Let's move on.

Tweezers act as a lever.

So the load acts on the object being picked up.

You squeeze here to produce the effort.

The end acts as a pivot.

Tweezers are not obvious levers.

The effort is applied between the load and the pivot.

Some levers are even harder to spot.

For example, a steering wheel acts as a lever.

An effort force is used to turn the wheel.

So we can see that here.

And then we've got the wheel rotating around the center with the load acting at the center.

Over to you.

The image shows a wheel being used to steer a large boat.

Which two statements are correct?

A, the arrows show the load forces.

B, the arrows show that effort forces.

C, the pivot is at point Y.

Or D, the pivot is at point X.

What do you think?

You can pause the video here and click play once you've got the answers.

So what did you get?

If you got B and C, you are correct.

So the arrows are actually showing the effort forces.

So can you imagine the captain of the ship applying that force?

And then C, the pivot is at point Y.

Task B1, I'd like you to state which pictures show a lever.

Two, I'd like you to mark where the pivot is on each lever.

And three, I'd like you to lastly mark, where the effort force would be applied to each lever.

Pause the video here and click play once you've completed this.

So how did that go?

Well, you may have got something like this.

So yes, this image is of a lever and we can see where the pivot is.

This image is also a lever, it's a seesaw.

And the pivot is there with, and the orange arrow shows where the effort force would be applied.

Here we've got a steering wheel, the pivot is in the middle.

And then we've got the arrows showing where the forces would be applied again.

And we've got an extra lever there as well.

And this is also a lever we've got where the effort force would be applied.

Well done if you managed to identify all those key points.

Let's move on.

Lesson cycle three, we're now gonna be predicting the size of turning effects, let's begin, The effort and the load on a lever do not have to be the same size.

Most levers are designed to produce load forces greater than their effort force.

These are called force multipliers and they come in handy.

So for example, crowbar are an example of a force multiplier.

A small effort force can produce a very large load force.

The long lever can be used to lift heavy objects, small distances.

The size of the load force produced depends on the size of the effort force.

Increasing that effort increases the load force.

The size of the load force also depends on the distances between the forces and the pivot.

The load force increases when it is further from the pivot than the effort force.

The load force decreases if it is closer to the pivot than the effort force.

Over to you.

Which of these arrangements produces the largest load force on the ball?

Is it A, B, or C?

Have a look closely.

You could pause the video here, click play once you've completed this check for understanding.

So how did that go?

Well, you should have got B, as there is greater effort, this will produce the largest load force on the ball.

So in other words, a larger effort further from the pivot.

The load force produced by the blades of the scissors will be different along the length of the blades.

Large force close to the pivot, smaller force further from the pivot.

Back to you.

How can turning effect of a brake lever be increased?

Is it A, pulling it further from the pivot?

B, putting it closer to the pivot?

C, using a larger effort force?

Or D, using a smaller effort force?

What do you think?

You can pause the video here and click play when you've got the answer.

So what did you get?

If you got A and C, you are correct.

The turning effect of a brake lever can be increased by putting it further from the pivot and using a larger effort force.

Well done if you managed to get that correct.

Let's move on.

Task C, Hannah is trying to cut a sheet of metal with some tin snips.

She squeezes the snips in the middle of the handles.

One, I'd like you to label the load effort and pivot to show the parts of the levers of the tin snips.

And two, how can she increase the turning effect of the snips to increase the force on the wire?

You can pause the video here and click pay once you've completed this task.

So what did you get?

Well, this is how you should have labeled the tin snip.

So if you've got effort right there at the end, the pivot just there and then the load.

So for two to increase the turning effect of the snips, to increase the force on the wire, your ideas could have included squeezing with a greater force, squeezing further from the pivot, effort far from pivot, placing the metal close to the pivot.

So loading close to the pivot.

Well done for completing this task.

Let's move on.

Now let's summarize our learning.

So this lesson was all about levers.

You now understand that levers are simple machines that use the turning effect of forces.

A lever has a pivot, effort, force and load force.

And lastly, levers can act as force multipliers.

Thank you so much for joining me in this lesson, bye.