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# High School Freshman Physics Practice Test: Tension, acceleration, velocity etc.

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1. A plane leaves the airport and flies east at 109 miles/hour. 4.5 hour(s) later a second plane leaves east at 240 miles/hour. How long after taking off does the second plane overtake the first plane?

2. What is the tension on an elevator cable if the elevator (with a mass of 1209.3 kg) is traveling up at 4.2 m/s?

3. A ball thrown straight up with a velocity of 4.8 m/s. How long will it take to return to the thrower?

4. A ball is fired by a cannon from the top of a cliff as shown in the figure. Which of the paths would the cannon ball most closely follow?

a. 1
b. 5
c. 3
d. 4
e. There is no best selection to answer this question.
f. 2

5. The graph below depicts the force of a hydraulic hammer pushing on a roller coaster on a straight and level track with no friction. What is the change in momentum of the roller coaster on during the first 6.5 seconds?

6. A large truck collides head-on with a small compact car. During the collision:

a. the truck exerts a force on the car but the car does not exert a force on the truck.
b. the car exerts a greater amount of force on the truck than the truck exerts on the car.
c. neither exerts a force on the other, the car gets smashed simply because it gets in the way of the truck.
d. the truck exerts a greater amount of force on the car than the car exerts on the truck.
e. the truck exerts the same amount of force on the car as the car exerts on the truck.

7. Five students push a small car down the driveway. The momentum of the 1191.1 kg car is plotted as a function of time in the graph above and reaches 3000 kg m/s in 4 seconds. What is the average force of push by each student during the push?

8. A locomotive of mass 3532.8 is rigidly attached to a railroad car of mass 2487.3 riding without friction on a horizontal track. If the locomotive, which has a coefficient of static friction 0.6, exerts a force of 3933.1 N on the railroad car, what is the magnitude of the acceleration of the locomotive?

9. A bicycle accelerates from rest at 3.5 m/s2 for 1.6 seconds. What is the total distance traveled?

10. A jet flying at 206.0 km/hr travels between two cities in 1.5 hour(s). A turboprop flying the same route takes 5.5 hours. What is the speed of the turboprop?

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## SOLUTION This solution is FREE courtesy of BrainMass!

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1.
The first plane has T hours more flight time than the first one, hence the distance of the first airplane from the airport is:
(1.1)
The second plane distance from the airport is:
(1.2)
When the two planes meet, their distances from the airport are the same.
Equating (1.1) to (1.2) and solving for t gives:

(1.3)
Plugging in the numbers:

The second plane will meet the first 3 hours and 45 minutes after takeoff.
2.
If the elevator moves with constant speed, the total net force exerted on it is zero.
The only forces acting on the elevator are its weight Mg pointing down and the tension in the cable pointing up.
Therefore, the tension equals the weight.
The elevator's weight and the tension are:
(1.4)
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3.
The equation of motion of an object in a free fall, starting at with initial velocity is:
(1.5)
If the final height is the same as the initial height we can solve for the time:

(1.6)
Plugging in the numbers:

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4.

The second the ball leaves the cannon, there is only one force acing on it - gravity.
The ball will immediately have a downward component to its speed.
Therefore paths (2), (4) and (5) cannot represent the correct trajectory.
Path (1) is not the correct trajectory since he ball's height is quadratic with time (it accelerates downwards) while the horizontal displacement is linear with time (there is no force in the horizontal direction).
Path (1) is a straight line, meaning that the height is linear - which is not the case.
Therefore, the only possible path is path (3).
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5.
The rate of change in the momentum is the force:
(1.7)
Therefore:
(1.8)
When we integrate both sides we get:
(1.9)
The expression on the right is the area under the curve in the force-time graph.

In our case the area is a triangle and the area of this triangle is:
(1.10)
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Plugging in the numbers:

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6.
Newton's third law states that when a first body exerts a force F1 on a second body, the second body simultaneously exerts a force F2 = âˆ’F1 on the first body. This means that F1 and F2 are equal in magnitude and opposite in direction. Thus, in our case, the truck exerts the same amount of force on the car as the car exerts on the truck.

7.
The average force is given by:
(1.11)
The change in momentum is and the time interval is , thus the average force is:

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8.
The acceleration of the locomotive must be equal the acceleration of the car.
The only force acting on the car is the pull of the locomotive (there is no friction)
Therefore, according to Newton's second law the acceleration of the car (and the locomotive) is the ratio between the force F exerted on the car and its mass Mc:
(1.12)
Plugging in the numbers:

This is the acceleration of the locomotive as well.
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9.
The distance traveled by a body that starts with initial velocity and initial position and accelerates with acceleration a for time t is given by:
(1.13)
If we start from rest then and we can set the initial position as zero as well.
This gives:
(1.14)
Plugging in the numbers:

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10.
The distance between the cities according to the jet is:
(1.15)
But according to the turboprop, the distance is:
(1.16)
Of course these two distances are the same, so we can equate them and solve for :

(1.17)
Plugging in the numbers:

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