Show:
Basics
Momentum and Force
Conservation of Momentum
Calculations
100
What are the units for momentum?
kg x m/s
100
How is force and momentum related to each other?
The change in momentum over time equals the net force
100
What is the formula for the Conservation of Momentum for an inelastic collision?
m1 x v1i + m2 x v2i = (m1 + m2)vf
100
What is the momentum of an object with a mass of 500 g and a velocity of 400 cm/s?
2 kg x m/s
200
Why is it possible for two objects with different masses have equal momentum?
The object with the lower mass will have a higher velocity than the object with the higher mass
200
What is the definition (or formula) of impulse?
Two acceptable answers 1. Impulse = change in momentum 2. Impulse = Force x time
200
Why is the Conservation of Momentum basically a statement of Newton's third law?
Action Force = -(Reaction Force) (change in momentum for object 1)/time = -(change in momentum for object 2)/time The time is equal on both sides - you get the basic formula for the total initial momentum being equal to the total final momentum
200
An 0.5 kg object is dropped vertically from a building 20 m high. What is the momentum of the object just as it reaches the ground?
9.9 m/s
300
Give an example of a system (with two objects) in which both objects are stationary initially but mobile in the final state.
Answers will vary
300
Why are air bags potentially a life saver for adults in car accidents?
The air bags reduce the force applied to the passenger by lengthening the time interval of contact. Since force = change in momentum/time, a longer time interval helps.
300
Why is the recoil velocity for a cannon always opposite in sign from the velocity of the cannon ball being propelled?
The initial momentum of the system (cannon and cannon ball ) is zero. So this means that in order for the final momentum of the system to equal zero, both objects must have velocities in opposite directions.
300
An 2 kg object moving at a velocity of 5 m/s decelerates at a rate of 0.8 m/s^2. How long will it take the object to achieve a change of momentum of 6 kg x m/s?
3.75 seconds (there are different ways of calculating this) 1. 6 kgxm/s = 1.6 N (time), solve for time 2. 2 m/s = 5 m/s + (-0.8 m/s^2)t, solve for time
400
Why is momentum a vector?
Because momentum depends on velocity which has both direction and magnitude.
400
This question is obnoxious and relies on your recall for the formula for elastic force. Find the momentum formula in terms of the spring constant and velocity.
Since elastic force = k(x2-x1) and since momentum = force/time Momentum = k x velocity (velocity = displacement/time)
400
If the acceleration versus time graph for an object has a zero slope, describe the momentum of the object.
The object's momentum isn't changing since the velocity remains constant.
400
A 100 g projectile is launched at an angle of 30 degrees off the ground with a velocity of 3 m/s. What is the initial vertical momentum?
0.15 kg x m/s vy = vin x sin30 = 3 m/s x 0.5 = 1.5 m/s Vertical momentum = (0.1 kg) x (1.5 m/s)
500
It is possible to produce two different linear plots with different axes labels. Specify how you would label the axes for both of the graphs.
Graph 1: y-axis = momentum, x-axis = mass Graph 2: y-axis = momentum, x-axis = velocity
500
How can you graphically determine the net force applied to an object?
By finding the slope of the momentum versus time graph
500
Why is the horizontal momentum constant for a projectile?
No net force is acting in the horizontal direction on the projectile, so this means that the acceleration is zero, making the velocity constant.
500
A 50 g projectile is launched 60 degrees off the ground with an initial velocity of 10 m/s. Find the horizontal momentum.
0.25 kg x m/s vx = vin x cos60 = 10 m/s x 0.5 = 5 m/s Horizontal momentum = 0.05 kg x 5 m/s