1. Intro to Vectors
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Before you start on a course on 2D kinematics, it is important to undertones vectors, namely any dimension that has both a magnitude and a direction. The interactives allow you 'play' with vectors, to see how we add and subtract them |
interactives
This pHET animation is useful to see both how vectors can add graphical and also as components
A vector interactive developed in Geogebra by Tom Walsh
sample problem
coming soon
problems
A worksheet on vectors
2. Relative Motion Explained
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This video is simply a quick primer to relative motion. Its more of a discussion point for teachers to introduce the concept This video introduce kinematics, terms such as distance and displacement, speed and velocity, and how they relate. A good start before you get into the specifics of kinematics. Once you have watched this examine the sample problem as well as an excellent interactive by Tom Walsh |
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It is always helpful to attempt the problem first before looking at the sample solution
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A relative motion interactive developed in Geogebra by Tom Walsh
more problems
- An aeroplane has a velocity of 240 km/h north according to its instruments. A cross wind of 100 km/h is blowing from the west. Where will the aircraft be after two hours?
(520km , N23°E) - A boat travels at 10 m/s North relative to the water in a river where the current is 10 m/s west. Find the velocity of the boat relative to the river bank. (14m/s , NW)
- A sailor stands on the deck of the ship which is travelling at 20 km/h north. He looks up and sees an albatross flying at 28 km southeast relative to the ship. What is the velocity of the albatross relative to the ocean floor? (20km/h E)
- Three swimmers can swim equally fast related to the water. They have a race to see who can swim across the river in the least time. Swimmer A swim is perpendicular to the current and lands on the far side shore downstream because the current has swept him in that direction. Swimmer B swims upstream at an angle to the current and lands on the far shore directly opposite the starting point. Swimming C swims downstream at an angle to the current in an attempt to take advantage of the current. Who crosses the river in the least time? Account for your answer.
3. Projectile Motion Explained
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Projectile motion was first serious studies scientifically by Galileo. In essence its two separate motions as right angles to each other, one with a constant acceleration, the other at constant velocity. This video explores the concept with a number of sample situations |
sample problems
Here are two sample problems involving projectile motion.
In each case, it is worth attempting them before looking at the solution
In each case, it is worth attempting them before looking at the solution
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going deeper
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Assuming the simplified model where we ignore air resistance, why is 45° the angle for maximum range?
This video explores the mathematical reasoning Teachers in school teach that projectile motion forms a parabolic shape.
But is that really true? I argue that it's not, with evidence to support it. But I use the argument that when we teach anything in physics (and science in general) we, as teachers and scientists, are always making models of concepts, which by their very nature, are simplifications. And thus there is a reason why we teach that way. |
interactives
Use this pHET interactive to explore projectile motion further
A projectile motion interactive developed in Geogebra by Tom Walsh
more problems
- A bullet is fired from a rifle that is held 1.6 m above the ground in a horizontal position. The initial speed of the bullet is 1100 m/s. Find
(a) the time it takes for the bullet to strike the ground and
(b) the horizontal distance traveled by the bullet. (629m) - A major league pitcher can throw a baseball in excess of 41 m/s. If a ball is thrown horizontally at this speed, how much can it be expected to drop due to gravity by the time it reaches a catcher who is 17 m away from the point of release? Pitcher’s mounds are raised to compensate for this drop. (0.84m)
- A horizontal rifle is fired at a bull’s eye. The muzzle speed ofthe bullet is 670 m/s. The barrel is pointed directly at the center of the bull’s eye, but the bullet strikes the target 2.5 cm below the center. What is the horizontal distance between the end of the rifle and the bull’s eye?( 47.9 m)
- A jet fighter is traveling horizontally with a speed of 111 m/s at an altitude of 300 m, when the pilot accidentally releases an outboard fuel tank.
(a) How much time elapses before the tank hits the ground. (7.82s)
(b) What is the velocity of the tank (magnitude and direction) just before it hits the ground? (134.9 m/s)
4. How Well do you know Projectiles?
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more problems
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more problems
I have got these from a variety of source, some my own, some from elsewhere. Lots of practice here
- projectile practice
- projectiles 1 answers included
- projectiles 2
- projectiles 3