a) Draw a diagram of this situation. b) A car is moving along, a long straight f
ID: 1428955 • Letter: A
Question
a) Draw a diagram of this situation.
b) A car is moving along, a long straight freeway. At an instant 5 seconds after it passes a particular exit, it has a velocity of 32 m/s going due North. At an instant 10 seconds after it passed the same exit, it has a velocity 10m/s going due South. Take North to be the direction of positive displacement and calculate the average acceleration of the car between the two instants of time
An object moves clockwise around a circular track of circumference 300m at a constant speed of 10 m/s.
Draw a diagram of this situation.
Calculate the average velocity over the interval of time between the nine O’clock position and the twelve O’clock position.
Calculate the average velocity over the interval of time between the six O’clock position and the nine O’clock position.
A diligent group of Physics students are arguing about how to compare the velocities in parts b) and c). Which argument, if any, below is correct?
Billy-Jean says “The two average velocities are the same because the average speed of the object is the same in both cases.”
Crystal says, “The two average velocities are the same because the velocity of the object at every point around the track is the same.”
Bob says, “The average velocities in parts b) and c) are different because they have different directions”.
Jolene says, “The average velocities in parts b) and c) are the same because the object moves the same distance, in a straight line, from the start to end of the motion in both situations.
Kim says, “You can’t say because the position vectors of the start and end of the motions depend upon the origin from which you measure them. And, the displacements are the differences between the position vectors. So, the displacements depend upon the origin chosen.
Lucy says, “The average velocities in parts b) and c) are the same because the object has the same displacement in both situations.
Paul says, “The two average velocities are different because the motion starts from different places on the circle in the two situations.
A block is sliding down the frictionless ramp. The ramp is inclined at 30 to the horizontal.
Add vectors to the above diagram to show the acceleration due to gravity and the acceleration down the ramp.
Calculate it’s acceleration in the direction down the ramp. Hint: This is the component of the acceleration due to gravity parallel to the ramp. Take the direction of positive displacement to be parallel to the ramp and to the right.
Calculate the component of the acceleration due to gravity parallel to the ramp, if
the ramp is inclined at 15 degrees to the horizontal.
A boat is being paddled across a river, which runs exactly East-West. The sailors are a paddling with a constant velocity of 10 m/s due North. The river has a constant current of 5 m/s due West.
Draw a vector diagram that represents this situation. Label the vectors and define them in words.
Calculate the average velocity of the boat. Hint: Find the vector sum of the two vectors in your diagram.
What is the instantaneous velocity of the boat half-way across the river? Explain.
Explanation / Answer
Vi = initial velocity = 32 m/s
Vf = final velocity = 10 m/s
t = time = 10 sec
acceleration is given as
a = (Vf - Vi )/ t
a = (-10 - 32) / 10 = - 4.2 m/s2
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