Terminology
The sum of the forces is equal to zero. This can also look like the sum of the torques being equal to zero.
When the mass of an object cannot be neglected, how do we consider the torque cause by the force of gravity?
Find where the center of mass is on the object and place the force at that r value.
Consider a massless shelf with length of 2 meters. If a force of 20 N is applied downwards at the end of the shelf, what force needs to be applied upward at half the length of shelf to keep the shelf stable?
40 N
Two carts collide and completely stop. If cart 1 of mass 7 kg is moving with a velocity of +10 m/s, what is the initial velocity of cart 2 with a mass of 5 kg.
-14 m/s
A ball of mass 5 kg starts at rest at the top of a hill that is 10 m tall. As it reaches the bottom of the hill, how fast is the ball moving?
14 m/s
What is torque?
tau = I*alpha
or
tau = r*F*sin(theta)
When looking at a collision, what is the best choice for the system?
Both, or all, objects involved in the collision.
Consider a massless shelf with length 1.5 meters. Two forces of 15 N and 20 N are applied upwards at 0.4 meters and 0.9 meters respectively. If a force of 30 N is applied downwards to keep the shelf stable, where is it applied?
0.8 meters
Two carts collide, tangle together, and begin moving at a velocity of +2 m/s. If the first cart of mass 5kg is moving at +15 m/s, what is the initial velocity of the second cart of mass 4kg?
-14.25 m/s
Lets consider the same situation as the previous problem, but rather than looking at the bottom of the hill, what is the velocity halfway down the hill?
9.9 m/s
What is the impulse-momentum theorem?
pi + J = pf
If an impulse in a system is present, what must be true about the momentum of the system?
Momentum is not conserved
Consider a shelf of mass 3 kg and length of 1.2 m. If a force is applied at the end of the shelf, what is the magnitude of that force?
14.7 N
A car of mass 2000 kg is driving at 15 m/s and is hit by another vehicle. After the collision, the car is moving back at 4 m/s. What was the impulse applied by the other vehicle?
-38000 kgm/s
An object with mass of 10kg is moving at a velocity of +5 m/s. A force of 20 N is applied in the same direction of movement over a distance of 10 m. What is the final velocity of the object?
+25 m/s
What is the Work-Energy Theorem?
Ei + W = Ef
How do external forces change the energy of a system?
Through work
Consider a massless shelf with length 2 m held up by a string at 45 degrees from parallel. If a force pulls down on the shelf at 0.7 m with magnitude of 20 N, what is the tension force needed in the string to keep the shelf stable?
9.9 N
Consider the answer to the previous problem. If the collision occurred over a time period of 2 seconds, what is the average net force applied by the other vehicle?
-11000 N
A ball of mass 2 kg is rolling at a speed of 12 m/s. A forced of 50 N is applied on the top of the ball while the ball travels for 15 m. What is the final velocity of the ball?
12 m/s
What are all the types of energy we have learned so far(up until thermal energy)?
Ug, K, Usp
What happens if a force is applied perpendicular to the movement of an object?
Energy of the system does not change
Consider a shelf with mass of 9 kg and length of 3 meters, held up by a chain at 30 degrees from parallel. A force pulls down on the shelf at 1 m with magnitude of 30 N. What is the tension force in the chain to keep the shelf stable?
108.2 N
Over a time frame of 12 seconds, an applied force decreases from 16 N to 10 N. What is the impulse? If this impulse is applied to a cart of mass 6kg moving at 10 m/s, what will its final velocity be?
36 m/s
A wagon of mass 25 kg is initially at rest. Someone pulls the wagon by the handle at an angle of 35 degrees to get the wagon moving. After pulling the wagon for 20 meters, the wagon is moving at a velocity of 10 m/s. What is the force applied on the wagon?
76.3 N