MCAT Physical : Newton's Second Law
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Example Question #11 : Newton's Second Law
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
5m/s
20m/s
10m/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 : Newtonian Mechanics
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?
4000N
–8000N
40000N
–4000N
–2000N
–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 truck experiences the greater force and the greater acceleration
The car and the truck experience equal force and the car experiences greater acceleration
The car experiences the greater force and the greater acceleration
The truck experiences the greater force and the car experiences the greater acceleration
Both the car and the truck experience equal force and 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 #12 : Newton's Second Law
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 #13 : Newton's Second Law
A 
For this question we must use Newton's second law. We have to use the formula 
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