At a school competition, Abdul ran 100.0 m in 19.9 s. If, after reaching the finish line, he walked directly back to his starting point in 280.1 s, what is the magnitude of his average velocity for the 200.0 m? An object in free fall in the absence of air resistance has an acceleration of 9.8 m/s2. Which of the following statements are true for that object: An object is thrown up in the air, it moves upwards until it reaches a maximum height and then falls back towards the ground. Take upward direction to be positive. The displacement of the ball during a short time interval is: During a drag race, a dragster is initially travelling 12 m/s when it crosses the start line and it immediately begins to accelerate at 3.0 m/s2 [fwd] for 8 seconds. The car then travels at a constant velocity for the next 150 meters. After this time, the dragster slows down with an acceleration of 2.00 m/s2 [back] for 25 meters. What is the car's average velocity for the entire trip? In an old movie, two people on horseback are riding towards each other to embrace after being lost in the desert for several hours. They simultaneously spot each other when they are 250.0 m apart. They instantly begin accelerating towards one another at a rate of 0.250 m/s2 and 0.285 m/s2 respectively. At what position do these two people meet? Define the origin to be the initial position of one of the people.

At a school competition, Abdul ran 100.0 m in 19.9 s. If, after reaching the finish line, he walked directly back to his starting point in 280.1 s, what is the magnitude of his average velocity for the 200.0 m ?

Answer : 0 m / s.

An object in free fall in the absence of air resistance has an acceleration of 9.8 m/s². Which of the following statements are true for that object : The acceleration of the object is constant, but its speed and velocity keeps increasing.

An object is thrown up in the air, it moves upwards until it reaches a maximum height and then falls back towards the ground. Take upward direction to be positive. The displacement of the ball during a short time interval is : positive while the ball is moving up, and negative while the ball is falling down.

During a drag race, a dragster is initially travelling 12 m/s when it crosses the start line and it immediately begins to accelerate at 3.0 m/s² [fwd] for 8 seconds. The car then travels at a constant velocity for the next 150 meters. After this time, the dragster slows down with an acceleration of 2.00 m/s² [back] for 25 meters. What is the car's average velocity for the entire trip?

Answer : 12.16 m / s.

In an old movie, two people on horseback are riding towards each other to embrace after being lost in the desert for several hours. They simultaneously spot each other when they are 250.0 m apart. They instantly begin accelerating towards one another at a rate of 0.250 m/s2 and 0.285 m/s2 respectively. At what position do these two people meet? Define the origin to be the initial position of one of the people.

Answer : 116.8 m away from the initial position of the first one.

Step-by-step explanation

Average velocity = Total displacement / Total time

= ( 100 - 100 ) m / ( 19.9 + 280.1 ) s

= 0 m / s.

An object in free fall in the absence of air resistance falls with a constant acceleration and increasing speed.

Hence, correct option is : The acceleration of the object is constant, but its speed and velocity keeps increasing.

Since the upward direction is taken to be positive, the displacement of the ball during a short time interval is : positive while the ball is moving up, and negative while the ball is falling down.

The dragster is initially travelling v₁ = 12 m / s when it crosses the start line and it immediately begins to accelerate at a₁ = 3 m / s² [ fwd ] for t₁ = 8 seconds, travelling a distance of : d₁ = v₁t₁ + a₁t₁² / 2 = 12 x 8 + 3 x 8² / 2 = 192 m.

The car then travels at a constant velocity of v₂ = v_o + a₁t₁ = ( 12 + 3 x 8 ) = 36 m / s the next d₂ = 150 meters, for a time of t₂ = d₂ / v₂ = 150 / 36 = 4.17 s.

After this time, the dragster slows down with an acceleration of a₃ = 2 m / s² [ back ] for d₃ = 25 m in a time of : t₃ = v₂ / a₃ = 36 / 2 = 18 s.

Hence, v_avg = ( d₁ + d₂ + d₃ ) / ( t₁ + t₂ + t₃ )

= ( 192 + 150 + 25 ) m / ( 8 + 4.17 + 18 ) s

= 12.16 m / s.

The two people on horseback simultaneously spot each other when they are d = 250 m apart.

They instantly begin accelerating towards one another at a rate of a₁ = 0.25 m / s² and a₂ = 0.285 m / s² respectively.

Let the time after which they meet be t, and the distance of the point of meeting be s from the initial position of the first one.

Therefore, a₁t² / 2 + a₂t² / 2 = d

or, t² = d / ( a₁ / 2 + a₂ / 2 )

= 250 / ( 0.25 / 2 + 0.285 / 2 )

= 934.58

or, t = √ 934.58 = 30.57 s.

Hence, s = a₁t² / 2 = 0.25 x 30.57² / 2 = 116.8 m.