Objects that are moving tend to continue moving, while objects that aren't moving tend to remain at rest unless they're acted upon by some other force. This is called the law of inertia and it applies to driving. For example, when you're waiting for a green light on flat pavement at an intersection, your vehicle won't move unless you engage the engine or are otherwise pushed. If you are going right into a curve, Inertia will pull your vehicle to the center of the road, or possibly into an oncoming traffic lane. Safety belts work against inertia to keep you from being thrown forward

The Law of Inertia

An object in motion, remains in motion, in a straight line, at a constant speed, until acted upon by an unbalanced force, is what keeps a car going straight down the highway, with minimal steering effort.

Effect of Inertia on Driving

While driving, inertia keeps your vehicle moving unless the vehicle is acted upon by something, such as your brakes, the road surface, a fixed object (such as a tree), or another vehicle. Inertia also causes your body and loose objects in the car to keep moving forward if your vehicle comes to a sudden stop.

Inertia in Crashes

You may be injured because of the inertia and momentum of loose objects in your car which can fly through the air during a sudden stop. When you're stopped and hit from behind, your head tends to stay in place due to inertia while the rest of your body is pushed forward by the seat. This causes whiplash. Properly adjusting your headrest can reduce injury due to whiplash.

Inertia and Whiplash

If your vehicle is hit from behind while stopped, your head tends to stay in place due to inertia, while the rest of your body is pushed forward by the seat. This causes whiplash. Properly adjusting your headrest reduces injuries due to whiplash.

EXTRA QUESTIONS

1. If the fastest you can safely drive is 65 mi/h what is the longest time you can stop for dinner if you must travel 541 mi in 9.6h total?

If the fastest you can safely drive is 65 mi/h, what is the longest time you can stop for dinner if you must travel 541 mi in 9.6h total?

A.) 1.0 h

B.) 1.3 h

C.) 1.4 h

D.) You can't stop at all.

#2. If the fastest you can safely drive is 65 mi/h, what is the longest time you can stop for dinner if you must travel 569 mi in 9.5 h total?

A.) 0.75 h

B.) 0.90 h

C.) 0.60 h

D.) you can't stop at all.

#3. If the fastest you can safely drive is 65 mi/h, what is the longest time you can stop for dinner if you must travel 513 mi in 9.6 h total?

A.) 1.4 h

B.) 2.0h

C.) 1.7h

D.) you can't stop at all

#4. If the fastest you can safely drive is 65 mi/h. what is the longest time you can stop for dinner if you must travel 487 mi in 9.8 h total

If the fastest you can safely drive is 65 mi/h, what is the longest time you can stop for dinner if you must travel 488 mi in 9.8 h total?

A.) 1.8 h

B.) 2.3 h

C.) 2.8 h

D.) You can't stop at all.

#1 You're driving down the highway late one night at 20 m/s when a deer steps onto the road 47 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

This can easily be solved using one of the kinematic equations of motion.

Let's deal with the reaction time first. We know you reaction time is 0.50 s, and the car travels a distance of (20 m/s)(0.5 s) = 10 m in that time, leaving a distance of 47 m - 10 m = 37 m to the deer when you start braking.

Assuming your car decelerates at 10 m/s², the distance it takes to brake can be found using one of the kinematic equations:

u = initial velocity = 20 m/s

v = final velocity = 0 m/s

a = acceleration = -10 m/s²

d = distance = ?

v² = u² + 2ad, and since v = 0, 2ad = -u² so that d = -u²/2a = -(20 m/s²)/(2*-10 m/s²) = 20 m.

So the distance between deer and car at stopping is 37 m - 20 m = 17 m.

ANS: 17 m

What is the maximum speed you could have and still not hit the deer?

what about the maximum speed? We know u² = -2ad, and you have 37 m to stop in: the maximum initial speed possible is

u² = -2(-10 m/s²)(37 m) = 740 m²/s² and take the square root

u = 27.2 m/s.

ANS: 27.2 m/s.

#2 You're driving down the highway late one night at 20 m/s when a deer steps onto the road 48 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 18 m

What is the maximum speed you could have and still not hit the deer?

ANS: 27.6 m/s.

# 3You're driving down the highway late one night at 20 m/s when a deer steps onto the road 37 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 7 m

What is the maximum speed you could have and still not hit the deer?

ANS: 23.2 m/s.

#4 You're driving down the highway late one night at 21 m/s when a deer steps onto the road 38 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 5.95 m

What is the maximum speed you could have and still not hit the deer?

ANS: 24.25 m/s.

#5 You're driving down the highway late one night at 20 m/s when a deer steps onto the road 58 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 28 m

What is the maximum speed you could have and still not hit the deer?

ANS: 30.9 m/s.

#6 You're driving down the highway late one night at 20 m/s when a deer steps onto the road 54 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 24 m

What is the maximum speed you could have and still not hit the deer?

ANS: 29.6 m/s.

#7 You are driving down the highway late one night at 20 m/s when a deer steps onto the road 35 m in front of you. your reaction time before stepping on the brakes is 0.50 s , and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 5 m

What is the maximum speed you could have and still not hit the deer?

ANS: 22.37 m/s.

#8 You're driving down the highway late one night at 15 m/s when a deer steps onto the road 42 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 12 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 20.6 m

What is the maximum speed you could have and still not hit the deer?

ANS: 21.2 m/s.

Unstable traffic flow occurs when drivers accelerate and brake too often. Unstable traffic flow wastes energy. The table below gives one example of traffic speeds, in kilometers per hour (km/h), in an unstable flow situation. What is the mean speed, in km/h, in this situation? You may use the calculator. A: 20

B: 30

C: 40

D: 50

The Law of Inertia

An object in motion, remains in motion, in a straight line, at a constant speed, until acted upon by an unbalanced force, is what keeps a car going straight down the highway, with minimal steering effort.

Effect of Inertia on Driving

While driving, inertia keeps your vehicle moving unless the vehicle is acted upon by something, such as your brakes, the road surface, a fixed object (such as a tree), or another vehicle. Inertia also causes your body and loose objects in the car to keep moving forward if your vehicle comes to a sudden stop.

Inertia in Crashes

You may be injured because of the inertia and momentum of loose objects in your car which can fly through the air during a sudden stop. When you're stopped and hit from behind, your head tends to stay in place due to inertia while the rest of your body is pushed forward by the seat. This causes whiplash. Properly adjusting your headrest can reduce injury due to whiplash.

Inertia and Whiplash

If your vehicle is hit from behind while stopped, your head tends to stay in place due to inertia, while the rest of your body is pushed forward by the seat. This causes whiplash. Properly adjusting your headrest reduces injuries due to whiplash.

EXTRA QUESTIONS

1. If the fastest you can safely drive is 65 mi/h what is the longest time you can stop for dinner if you must travel 541 mi in 9.6h total?

If the fastest you can safely drive is 65 mi/h, what is the longest time you can stop for dinner if you must travel 541 mi in 9.6h total?

A.) 1.0 h

B.) 1.3 h

C.) 1.4 h

D.) You can't stop at all.

**Click here to reveal the Answer**

1.3h

EXPLANATION: Only Calculation

541 mi / 65 mi/h = 8.3 h

9.6 h - 8.3 h = 1.3h

EXPLANATION: Only Calculation

541 mi / 65 mi/h = 8.3 h

9.6 h - 8.3 h = 1.3h

#2. If the fastest you can safely drive is 65 mi/h, what is the longest time you can stop for dinner if you must travel 569 mi in 9.5 h total?

A.) 0.75 h

B.) 0.90 h

C.) 0.60 h

D.) you can't stop at all.

**Click here to reveal the Answer**

0.75 h

EXPLANATION: Only Calculation

569 mi / 65 mi/h = 8.75 h

9.5 h - 8.75 h = 0.75 h

EXPLANATION: Only Calculation

569 mi / 65 mi/h = 8.75 h

9.5 h - 8.75 h = 0.75 h

#3. If the fastest you can safely drive is 65 mi/h, what is the longest time you can stop for dinner if you must travel 513 mi in 9.6 h total?

A.) 1.4 h

B.) 2.0h

C.) 1.7h

D.) you can't stop at all

**Click here to reveal the Answer**

1.7h

EXPLANATION: Only Calculation

513 mi / 65 mi/h = 7.89 h = 7.9 h

9.6 h - 7.9 h = 1.7h

EXPLANATION: Only Calculation

513 mi / 65 mi/h = 7.89 h = 7.9 h

9.6 h - 7.9 h = 1.7h

#4. If the fastest you can safely drive is 65 mi/h. what is the longest time you can stop for dinner if you must travel 487 mi in 9.8 h total

If the fastest you can safely drive is 65 mi/h, what is the longest time you can stop for dinner if you must travel 488 mi in 9.8 h total?

A.) 1.8 h

B.) 2.3 h

C.) 2.8 h

D.) You can't stop at all.

**Click here to reveal the Answer**

2.3 h

EXPLANATION: Only Calculation

488 mi / 65 mi/hr = 7.51 hours.

9.8 – 7.5 = 2.3 hr.

EXPLANATION: Only Calculation

488 mi / 65 mi/hr = 7.51 hours.

9.8 – 7.5 = 2.3 hr.

#1 You're driving down the highway late one night at 20 m/s when a deer steps onto the road 47 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

This can easily be solved using one of the kinematic equations of motion.

Let's deal with the reaction time first. We know you reaction time is 0.50 s, and the car travels a distance of (20 m/s)(0.5 s) = 10 m in that time, leaving a distance of 47 m - 10 m = 37 m to the deer when you start braking.

Assuming your car decelerates at 10 m/s², the distance it takes to brake can be found using one of the kinematic equations:

u = initial velocity = 20 m/s

v = final velocity = 0 m/s

a = acceleration = -10 m/s²

d = distance = ?

v² = u² + 2ad, and since v = 0, 2ad = -u² so that d = -u²/2a = -(20 m/s²)/(2*-10 m/s²) = 20 m.

So the distance between deer and car at stopping is 37 m - 20 m = 17 m.

ANS: 17 m

What is the maximum speed you could have and still not hit the deer?

what about the maximum speed? We know u² = -2ad, and you have 37 m to stop in: the maximum initial speed possible is

u² = -2(-10 m/s²)(37 m) = 740 m²/s² and take the square root

u = 27.2 m/s.

ANS: 27.2 m/s.

#2 You're driving down the highway late one night at 20 m/s when a deer steps onto the road 48 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 18 m

What is the maximum speed you could have and still not hit the deer?

ANS: 27.6 m/s.

# 3You're driving down the highway late one night at 20 m/s when a deer steps onto the road 37 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 7 m

What is the maximum speed you could have and still not hit the deer?

ANS: 23.2 m/s.

#4 You're driving down the highway late one night at 21 m/s when a deer steps onto the road 38 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 5.95 m

What is the maximum speed you could have and still not hit the deer?

ANS: 24.25 m/s.

#5 You're driving down the highway late one night at 20 m/s when a deer steps onto the road 58 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 28 m

What is the maximum speed you could have and still not hit the deer?

ANS: 30.9 m/s.

#6 You're driving down the highway late one night at 20 m/s when a deer steps onto the road 54 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 24 m

What is the maximum speed you could have and still not hit the deer?

ANS: 29.6 m/s.

#7 You are driving down the highway late one night at 20 m/s when a deer steps onto the road 35 m in front of you. your reaction time before stepping on the brakes is 0.50 s , and the maximum deceleration of your car is 10 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 5 m

What is the maximum speed you could have and still not hit the deer?

ANS: 22.37 m/s.

#8 You're driving down the highway late one night at 15 m/s when a deer steps onto the road 42 m in front of you. Your reaction time before stepping on the brakes is 0.50 s, and the maximum deceleration of your car is 12 m/s2 . how much distance is between you and the deer when you come to a stop?

How much distance is between you and the deer when you come to a stop?

ANS: 20.6 m

What is the maximum speed you could have and still not hit the deer?

ANS: 21.2 m/s.

Unstable traffic flow occurs when drivers accelerate and brake too often. Unstable traffic flow wastes energy. The table below gives one example of traffic speeds, in kilometers per hour (km/h), in an unstable flow situation. What is the mean speed, in km/h, in this situation? You may use the calculator. A: 20

B: 30

C: 40

D: 50

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