Greater force is needed to stop car because it has higher inertia brainly

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Inertia was best explained by Sir Isaac Newton in his first law of motion. Basically, the law of motion states that an object at rest stays at rest, and an object in motion continues in motion until an external force acts on it. Examine several examples of inertia.

Balls rolling down ramp inertia example

When it comes to laws of motion, inertia is one of the greats. Inertia resists change in motion. Objects want to stay in rest or motion unless an outside force causes a change. For example, if you roll a ball, it will continue rolling unless friction or something else stops it by force. You can also think about the way that your body keeps moving forward when you hit the brake on your bike. Inertia comes in different types, check them out.

In inertia, there isn’t just one type. Instead, you’ll find three different types of inertia including:

Inertia of rest - An object stays where it is placed, and it will stay there until you or something else moves it. (i.e. Dust particles stay at rest until you shake a carpet.)
Inertia of motion - An object will continue at the same speed until a force acts on it. (i.e. Body going forward when a car stops.)
Inertia of direction - An object will stay moving in the same direction unless a force acts on it. (i.e. One's body movement to the side when a car makes a sharp turn.)

Reading about inertia is great but to understand one of Newton’s laws of motion, you’ll want to look at examples.

Now that you know what inertia of rest is, explore several examples.

If pulled quickly, a tablecloth can be removed from underneath the dishes. The dishes have the tendency to remain still as long as the friction from the movement of the tablecloth is not too great.
If a stopped car is hit by a moving car from behind, the passengers inside may experience whiplash as a result of the body moving forward but the head lagging behind. The head is experiencing inertia.
A balloon in a car will appear to move when the car moves forward, but the balloon is actually attempting to stay in the place it was, it is only the car that is moving.
When a car is abruptly accelerated, drivers and passengers may feel as though their bodies are moving backward. In reality, inertia is making the body want to stay in place as the car moves forward.
If an index card is placed on top of a glass with a penny on top of it, the index card can be quickly removed while the penny falls straight into the glass, as the penny is demonstrating inertia.
When pulling a Band-Aid off, it is better to pull it fast. Your skin will remain at rest due to inertia, and the force pulls the Band-Aid off.

Objects in motion stay in motion or want to, just like these examples.

Seat belts tighten in a car when it stops quickly.
Men in space find it more difficult to stop moving because of a lack of gravity acting against them.
When playing football, a player is tackled, and his head hits the ground. The impact stops his skull, but his brain continues to move and hit the inside of his skull. His brain is showing inertia.
If one drove a car directly into a brick wall, the car would stop because of the force exerted upon it by the wall. However, the driver requires a force to stop his body from moving, such as a seatbelt. Otherwise, inertia will cause his body to continue moving at the original speed until his body is acted upon by some force.
When a baseball is thrown, it will continue to move forward until acted upon by gravity. The greater the force of the throw, the harder it is for gravity to act upon it.
A hockey puck will continue to slide across the ice until acted upon by an outside force.
When pedaling a bicycle, if you stop pedaling, then the bike continues going until friction or gravity slows it down.
A car that is moving will continue, even if you switch the engine off.
If a ball is on a slanted surface and you let go, gravity will make it roll down the slope. It has inertia, and if there is a level area at the bottom of the slope, it will continue moving.
When entering a building through a rotating door, inertia will allow the door to hit you in the back if you don't get out of the way.
If you are rolling a cart with something on top and you hit something that makes the cart stop, what is on top may fall off.
It is harder to stop a big vehicle, like a bus, than a smaller vehicle, like a motorcycle. There is more inertia with the larger object.
A concussion occurs because your brain is still moving while the outside skull is stopped. This is what causes the injury.
If you are on a train and the train is moving at a constant speed, a toy tossed into the air will go straight up and then come down. This is because the toy has inertia like the train and you.
If a car is moving forward it will continue to move forward unless friction or the brakes interfere with its movement.

View how objects stay in the same direction unless another force is applied. Examine examples of inertia of direction.

Hovercraft can be a challenge to manipulate because, unlike cars, they do not have the same level of friction, so inertia causes the hovercraft to want to continue in its same direction without stopping or turning.
Abruptly stopping a cart with an object on top causes the object on top to fall off. Inertia causes this by making the object want to continue moving in the direction that it was.
If you jump from a car or bus that is moving, your body is still moving in the direction of the vehicle. When your feet hit the ground, the grounds act on your feet and they stop moving. You will fall because the upper part of your body didn't stop, and you will fall in the direction you were moving.
When you stir coffee or tea and stop, the swirling motion continues due to inertia.
Objects that establish orbit around the earth, such as satellites, continue on their trajectory due to inertia.
If you throw a rock straight up, it will not vary from its direction.
Inertia enables ice skaters to glide on the ice in a straight line.
If the wind is blowing, a tree's branches are moving. A piece of ripe fruit that falls from the tree will fall in the direction the wind is moving because of inertia.
Space probes are launched to get past the Earth's atmosphere. Then, they coast due to inertia.

See if you can recognize inertia when it occurs over the course of your day. You might be surprised at how much you notice moments of inertia in your life. If you’re geeked about scientific principles, try out examples of gas to solid.

Staff Writer

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Balanced and Unbalanced Forces in the World Around You
The concept of force is an important topic related to basic physics. A force is simply the push or pull that occurs when an object interacts with other things in its surroundings. Forces can cause objects to stay still, to move at a set rate, to speed up, or to slow down. The impact a force has on an object is based on whether the force is balanced or unbalanced. Discover basic facts about balanced and unbalanced forces.

It may not seem like much, but driving even a few kilometres per hour above the speed limit greatly increases the risk of an accident.

Many of us cheat a little when driving. We figure that while the speed limit is 60 km/h the police won't pull us over if we sit on 65. So we happily let the speedo hover just above the speed limit, unaware that by so doing we are greatly magnifying our chances of crashing.

Using data from actual road crashes, scientists at the University of Adelaide estimated the relative risk of a car becoming involved in a casualty crash—a car crash in which people are killed or hospitalised—for cars travelling at or above 60 km/h. They found that the risk approximately doubled for every 5 km/h above 60 km/h. Thus, a car travelling at 65 km/h was twice as likely to be involved in a casualty crash as one travelling at 60 km/h. For a car travelling at 70 km/h the risk increased fourfold. For speeds below 60 km/h the likelihood of a fatal crash can be expected to be correspondingly reduced.

Stopping distance calculator

Small conditions can make a big difference to the time it takes you to stop your car, such as going a few km/hr slower or being alert on the road.

Interactive

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metres travelled before car stops

metres travelled before brakes are fully applied

One reason for this increased risk is reaction time—the time it takes between a person perceiving a danger and reacting to it. Consider this example. Two cars of equal weight and braking ability are travelling along the same road. Car 1, travelling at 65 km/h, is overtaking Car 2, which is travelling at 60 km/h. A child on a bicycle—let's call him Sam—emerges from a driveway just as the two cars are side-by-side. The drivers both see the child at the same time and both take 1.5 seconds before they fully apply the brakes. In those few moments, Car 1 travels 27.1 metres and Car 2 travels 25.0 metres.

The difference of 2.1 metres might seem relatively small, but combined with other factors it could mean the difference between life and death for Sam.

The figure of 1.5 seconds is the reaction time of average drivers. A driver who is distracted, for example listening to loud music, using a mobile phone or has drunk alcohol may take as long as 3 seconds to react.

Braking distance

The braking distance (the distance a car travels before stopping when the brakes are applied) depends on a number of variables. The slope or grade of the roadway is important—a car will stop more quickly if it is going uphill because gravity will help. The frictional resistance between the road and the car's tyres is also important—a car with new tyres on a dry road will be less likely to skid and will stop more quickly than one with worn tyres on a wet road. If slope and frictional resistance are equal, the factor that has most influence on braking distance is initial speed.

The formula used to calculate braking distance can be derived from a general equation of physics:

$$V_{f}^{2} = V_{0}^{2} - 2ad$$

where Vf is the final velocity, V0 is the initial velocity, a is the rate of deceleration and d is the distance travelled during deceleration. Since we know that Vf will be zero when the car has stopped, this equation can be re-written as:

$$d = V_{0}^{2} / 2a$$

From this we can see that braking distance is proportional to the square of the speed—which means that it increases considerably as speed increases. If we assume that a is 10 metres per second per second and assume that the road is flat and the braking systems of the two cars are equally effective, we can now calculate braking distance for cars 1 and 2 in our example. For car 1, d = 16.3 metres, while for Car 2, d = 13.9 metres.

Adding reaction distance to braking distance, the stopping distance for Car 1 is 27.1 + 16.3 = 43.4 metres. For Car 2, stopping distance is 25 + 13.9 = 38.9 metres. Car 1 therefore takes 4.5 more metres to stop than Car 2, a 12 per cent increase.

We can now see why Car 1 is more likely than Car 2 to hit Sam. If Sam is 40 metres from the cars when the drivers see him, Car 2 will stop just in time. Car 1, though, will plough straight into him. By re-writing the first equation, we can calculate the speed at which the collision occurs:

$$V_{f} = \sqrt{V_{0}^{2} - 2ad} = 8.2\mbox{ }metres\mbox{ }per\mbox{ }second$$

(where d = 40 metres minus the reaction distance of 27.1 metres = 12.9 metres).

Thus, the impact occurs at about 30 kilometres/hour, probably fast enough to kill Sam. If the car's initial speed was 70 kilometres/hour, the impact velocity would be 45 kilometres/hour, more than fast enough to kill.

These calculations assume that the driver has an average reaction time. If the driver is distracted and has a longer than average reaction time, then he or she may hit Sam without having applied the brakes at all.

Impact on a pedestrian

Because the pedestrian, Sam, is so much lighter than the car, he has little effect upon its speed. The car, however, very rapidly increases Sam's speed from zero to the impact speed of the vehicle. The time taken for this is about the time it takes for the car to travel a distance equal to Sam's thickness—about 20 centimetres. The impact speed of Car 1 in our example is about 8.2 metres per second, so the impact lasts only about 0.024 seconds. Sam must be accelerated at a rate of about 320 metres per second per second during this short time. If Sam weighs 50 kilograms, then the force required is the product of his mass and his acceleration—about 16,000 newtons or about 1.6 tonnes weight.

Since the impact force on Sam depends on the impact speed divided by the impact time, it increases as the square of the impact speed. The impact speed, as we have seen above, increases rapidly as the travel speed increases, because the brakes are unable to bring the car to a stop in time.

Once a pedestrian has been hit by a car, the probability of serious injury or death depends strongly on the impact speed. Reducing the impact speed from 60 to 50 kilometres/hour almost halves the likelihood of death, but has relatively little influence on the likelihood of injury, which remains close to 100 per cent. Reducing the speed to 40 kilometres/hour, as in school zones, reduces the likelihood of death by a factor of 4 compared with 60 kilometres/hour, and of course the likelihood of an impact is also dramatically reduced.

Modern cars with low streamlined bonnets are more pedestrian-friendly than upright designs, such as those found in 4-wheel drive vehicles, since the pedestrian is thrown upwards towards the windscreen with a corresponding slowing of the impact. Cars with bull-bars are particularly unfriendly to pedestrians and to other vehicles, since they are designed to protect their own occupants with little regard for others.

Impact on a large object

If, instead of hitting a pedestrian, the car hits a tree, a brick wall, or some other heavy object, then the car’s energy of motion (kinetic energy) is all dissipated when the car body is bent and smashed. Since the kinetic energy (E) is given by

$$E = (1/2)\mbox{ }mass × speed^{2}$$

it increases as the square of the impact velocity. Driving a very heavy vehicle does not lessen the effect of the impact much because, although there is more metal to absorb the impact energy, there is also more energy to be absorbed.

Less control

At higher speeds cars become more difficult to manoeuvre, a fact partly explained by Newton's First Law of Motion. This states that if the net force acting on an object is zero then the object will either remain at rest or continue to move in a straight line with no change in speed. This resistance of an object to changing its state of rest or motion is called inertia . It is inertia that will keep you moving when the car you are in comes to a sudden stop (unless you are restrained by a seatbelt).

To counteract inertia when navigating a bend in the road we need to apply a force—which we do by turning the steering wheel to change the direction of the tyres. This makes the car deviate from the straight line in which it is travelling and go round the bend. The force between the tyres and the road increases with increasing speed and with the sharpness of the turn (Force = mass × velocity squared, divided by the radius of the turn), increasing the likelihood of an uncontrolled skid. High speed also increases the potential for driver error caused by over- or under-steering (turning the steering wheel too far, thereby ‘cutting the corner’, or not far enough, so that the car hits the outside shoulder of the road).

Killer speed

All these factors show that the risk of being involved in a casualty crash increases dramatically with increasing speed. In the University of Adelaide study referred to earlier, this was certainly true in zones where the speed limit was 60 kilometres/hour: the risk doubled with every 5 kilometres/hour above the speed limit. A corresponding decrease is to be expected in zones with lower speed limits.

Source: RiAus on YouTube. View video details and transcript.

You decide on your speed, but physics decides whether you live or die. TAC Road Safety Commercial

Is the risk worth it? In our hypothetical case, the driver of Car 2, travelling at the speed limit, would have had a nasty scare, but nothing more. The driver of Car 1, driving just 5 kilometres/hour above the limit, would not be so lucky: whether Sam had lived or died, the driver would face legal proceedings, a possible jail sentence, and a whole lifetime of guilt.