MCAT Physical : Newtonian Mechanics and Motion
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Example Questions
Example Question #1 : Newton's Second Law
A 
An elevator car with its counterweight is a crude example of an Atwood machine, the device described in this question. The acceleration in an Atwood machine varies between zero (the masses are equal) and the full value of gravitational acceleration (one mass is very near zero and the other is very large).
Here, the total mass being accelerated is the sum of the two, or 0.3 kg, so the trick is to find the net force acting on the masses. Although the formal presentation in physics texts looks daunting, just consider that one mass is attempting to fall by pulling up on the other mass, and vice versa. Each experiences a downward force due to gravity:
This force is transmitted through the string to an upward force on the opposite mass. The net force is simply the gravitational force acting on one mass minus that acting on the other:
Now that we know the net force and the total mass, we can determine the acceleration using Newton's second law:
You can easily substitute in numbers to see why the Atwood machine has possible solutions between 
Example Question #241 : Newtonian Mechanics And Motion
A 
The force in the string is all generated by the suspended 
Using this force, we can determine the acceleration on the total mass of the system. The total mass being accelerated is:
Use Newton's second law to calculate the acceleration of the system.
Note that the net force and acceleration are negative, indicating that the net movement will be in the downward direction.
It is important to understand that even if the block cannot provide a frictional force to resist being pulled to the right, it still has to be accelerated; Newton's second law is obeyed in frictionless and gravity-free situations (like outer space). This issue is well demonstrated with an Atwood machine.
Example Question #1 : Ap Physics 1
If a 15kg object is subjected to a force of 175N to the east and another force of 1020N to the west, what is the object’s acceleration?
113m/s2
1.4m/s2
5.6m/s2
56m/s2
56m/s2
First, find the net force by subtracting the opposing forces.
F = 1020N – 175N = 845 N to the west
Next, find acceleration using Newton's second law, 
Example Question #2 : Newton's Second Law
A basketball is thrown in the air with an initial velocity of 
The acceleration cannot be determined without know the force on the ball
The acceleration is constant
Just before the ball lands
At the highest point in the ball's path
Just after being thrown
The acceleration is constant
The only force acting on the ball at any point during flight is the downwards force of gravity, which is constant. There are no forces acting on the ball in the horizontal direction. Any acceleration will result in a force, according to Newton's second law.
If there are no other forces, then we can assume that there are no other accelerations acting on the ball. Acceleration due to gravity is constant. If this is the only acceleration on the ball, then the acceleration must be constant throughout flight.
Example Question #2 : Newton's Second Law
What is the acceleration due to gravity on a planet on which an object with a mass of 20.0kg has a weight of 270N?
0.074m/s2
13.5m/s2
10m/s 2
27m/s2
13.5m/s2
Solve the following equation for acceleration, using the values given in the question.
Example Question #241 : Newtonian Mechanics And Motion
A 2kg lead ball is loaded into a spring cannon and the cannon is set at a 45º angle on a platform. The spring has a spring constant of 100N/m and the ball and spring system is compressed by 1m before launch. While the ball is in flight air resistance can be neglected, and the ball finishes its flight by landing at a cushion placed some distance away from the cannon.
When the ball leaves the cannon, how fast is it traveling?
9m/s
10m/s
20m/s
5m/s
10m/s
Think back to the 3 main kinematics equations that we know:
vf2 = vi2 + 2aΔx
vf = vi + at
Δx = vit + ½at2
Newton’s second law can be used in combination with the spring force equation to solve for the acceleration of the system. Remember that any force, whether it is kinematic, electrical, or gravitational, is equal to Newton’s second law.
Fspring = kx = masystem
Now we need to choose which equation gives us the final velocity, given that we know the acceleration and the change in position (1m).
vf2 = vi2 + 2aΔx
vf2 = (0 m/s)2 + 2(50 m/s2)(1 m) = 100 m2/s2
Example Question #1 : Ap Physics B
A car moving at 40m/s suddenly applies a braking force and comes to rest in 20s, with constant deceleration. If the car has a mass of 2000kg, what is the braking force?
40000N
4000N
–8000N
–2000N
–4000N
–4000N
First we can calculate the acceleration.
Using F = ma with the magnitude of the acceleration we can find the force.
Example Question #1 : Newton's Second Law
A 2000kg car with a velocity of 
The car and the truck experience equal force and the car experiences greater acceleration
Both the car and the truck experience equal force and acceleration
The truck experiences the greater force and the greater acceleration
The truck experiences the greater force and the car experiences the greater acceleration
The car experiences the greater force and the greater acceleration
The car and the truck experience equal force and the car experiences greater acceleration
The car and the truck experience equal and opposite forces, but since the car has a smaller mass it will experience greater acceleration than the truck according to the equation F = ma.
A greater mass will decrease the acceleration.
Example Question #241 : Newtonian Mechanics And Motion
A force of 
The block moves with a constant velocity
For this question we must use Newton's second law. We have to use the formula 
Example Question #422 : Mcat Physical Sciences
A 
For this question we must use Newton's second law. We have to use the formula 
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