# 5 Examples of Uniform Rectilinear Motion

The uniform rectilinear motion (MRU) It is a movement that is carried out on a straight line, at constant speed (with constant magnitude and direction).

The path that an object describes as it moves from one point to another is called a path. Physics classifies movements by their trajectory:

Rectilinear. It is done in one direction only.

• Uniform. The speed is constant, its acceleration is zero.
• Accelerated. The constant acceleration, that is to say that the speed increases or decreases in a constant way.

Curved.

• Pendular. It is an oscillatory movement, like that of a pendulum.
• Circular. With axis of rotation and constant radius. The path of motion describes a circumference.
• Parabolic. The object’s path draws a parabola.

That a movement is uniform means that its speed is constant, its speed does not change. Acceleration is zero.

Speed ​​is a quantity that is defined as the distance traveled in a unit of time. For example: 40 kilometers per hour means that the mobile travels 40 kilometers in an hour (40 km / h).

To calculate the distance traveled by an object with uniform rectilinear motion, the following data are used: speed and time. If you know the distance and the speed but you want to calculate the time it will take, divide the distance by the speed:

d / v = t 50 km / 100 km / h = 1/2 h (0.5 h)

You can also find out the speed if you have the distance and time data:

D / t = V 50 km / ½ h = 100 km / h

In other words, the characteristics of the uniform rectilinear motion (MRU) are:

• Straight path
• Constant speed (uniform)
• Zero acceleration
• Constant direction

### Examples of uniform rectilinear motion

1. A train leaves Paris at 6 am and arrives in Lyon at 8 am. Its route is in a straight line. The distance between Gare de Paris and Gare de Lyon is 400 km. The train always goes at the same speed, without accelerating or braking until it reaches its destination. How fast is the train going?

Distance: 400 km

Weather: 8 hours – 6 hours = 2 hours

400 km / 2 hrs = 200 km / h

Answer: the train goes at 200 kilometers per hour.

1. The route from my house to my friend’s house is a straight line. Whenever I visit it, I drive my car at a speed of 20 kilometers per hour, without speeding up or slowing down until I get there. It takes me half an hour to get there.

How far is my friend’s house?

Speed: 20 km / h

Weather: 1/2 h

20 km / h / 1/2 h = 10 km

Answer: my friend’s house is ten kilometers away.

1. Juan delivers newspapers in his neighborhood. Since he knows the addresses by heart, he gets on his bike and makes his way without stopping when he reaches each house, instead he throws the newspapers from the bike. Juan’s route is along a single, straight street, of 2 km. It goes at a speed of 10 kilometers per hour. Juan must start the tour and then go back down the same street at the same speed. If Juan leaves now, how long will it take to return?

In this case there are two uniform rectilinear movements: the one going and the one back.

Speed: 10 km / h

Distance: 2 km

2 km / 10 km / h = 0.2 h = 12 minutes

This calculation is only for one of the tours.

12 minutes x 2 (round trip) = 24 minutes

Answer: Juan will take 24 minutes to return.

1. Every morning I run ten kilometers straight along the beach, and it takes me 1 hour. I want to improve my speed to play a race against my competitor, who can run at 12 kilometers per hour. How long does it take for me to do my usual ride to get up to speed with my competitor?

Speed: 12 km / h

Distance: 10 km

10 km / 12 km / h = 0.83 h = 50 minutes

Answer: I must finish the course in 50 minutes to be as fast as my competitor.