HESI A2 Exam: Displacement, Velocity and Acceleration
• What signifies how fast an object is moving and in what direction it is moving?
• What is the formula for force? What about net force?
• How do you find displacement?
• Given constant acceleration, what is the formula for velocity?
Intro
Velocity signifies how fast an object is moving and in what direction it is moving.
Speed does not take into account the direction in which an object is moving.
Acceleration is the change of velocity as time elapses.
Deceleration is simply a special case of acceleration that causes an object to slow down.
Force = mass x acceleration
If we are told that an object has a mass of 500 kg, starts from rest, and reaches a velocity of 15 m/s in 10 seconds, then what is the force acting upon the object?
We already know that the mass is 500 kg. We need to find the acceleration, and then multiply that by 500 to find the force.
a = v2 - v1/t
a = (15 - 0)/10 = 1.5
500(1.5) = 750 m/s^2
Displacement and Average Velocity
Displacement along a straight line has both magnitude and direction. The formula for displacement = final position - original position. A key point to remember is that displacement only takes into account final and original position, not total distance traveled. So, if you ran around a track and finished right where you started, your displacement would be 0 feet.
Average velocity = displacement/change in time.
Constant Acceleration
Starting from rest, a car accelerates in one direction at a constant rate of 20 feet per second. What is the instantaneous speed after five seconds?
Given constant acceleration, the formula for velocity is v = v0 + at. The car starts at rest, so v0 = 0.
v = 20(5)
v = 100 ft./s
Net Force
How much force is needed to accelerate a 750 kg vehicle 10 meters per second/per second?
Net force = mass x acceleration. The mass is 750 kg and the acceleration is 10 m/s. Multiply those two together and you get 7,500 N. When mass is in kilograms and acceleration is in m/s/s, the unit of force is newtons (N).
Average Acceleration
30 seconds into her workout, Jennifer is traveling at 15 meters per second. At 40 seconds, she is traveling at 35 meters per second. What is her average acceleration from 30 to 40 seconds?
Acceleration equals the change in velocity divided by the change in time. The equation for this is a = (vf - vi) / (tf - ti).
a = (35 - 15)/(40 - 30)
20/10 = 2.0 m/s^2
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