The Kinematic Equations

Question 1

What does vi mean?

Answer 1

Initial velocity, how fast it’s going at the start of the problem.

Question 2

What does vf mean?

Answer 2

Final velocity, how fast it’s going at the end of the problem.

Question 3

What is the kinematic equation for finding vf?

Answer 3

vf = vi + at

Question 4

What is the kinematic equation for finding distance, using vi, t and a?

Answer 4

d = vit + 1/2at^2

Question 5

What is the kinematic equation for finding distance, using vi, vf, and t?

Answer 5

d = (vi + vf)/2 x t

Question 6

What is the kinematic equation for finding final velocity, using vi,a, and d?

Answer 6

vf^2 = vi^2 + 2ad

Question 7

What does vi equal when something is starting from rest?

Answer 7

vi = 0

Question 8

When an object is thrown upwards what is its velocity at the top of its path?

Answer 8

0

Question 9

When does an object have positive velocity?

Answer 9

When it’s going up.

Question 10

When does an object have negative velocity?

Answer 10

When it is going down.

Question 11

When an object is thrown what is its acceleration?

Answer 11

-9.8ms^-1

Question 12

A jogger runs 2km N then 3km E. What is the total distance the jogger has run?

Answer 12

5km

Question 13

A car travelling at 14.7ms^-1 accelerates over the course of a minute at a rate of -0.18ms^-2. Explain what the negative rate of acceleration means in terms of motion of the car.

Answer 13

The car’s speed is changing at a negative rate, which means it is slowing down.

Question 14

A student drops their phone from a bridge over a motorway. At what point in the fall does the phone have the greatest speed?

Answer 14

Just before it hits the ground.

Question 15

The student’s friend drops their sandwich at the same time as the student drops their phone. Assuming air resistance is negligible, which item will hit the ground first?

Answer 15

They both hit the ground at the same time. Both experience the same constant acceleration
due to gravity so they fall at the same rate.

Question 16

A seagull drops a chip into the sea, the chip submerges before floating back up to the surface. Describe the motion of the chip in the water.

Answer 16

After the chip hits the water it decelerates (accelerates upwards) due to the buoyancy force opposing gravity. Once the speed reaches zero, the chip continues to accelerate in the same direction until it reaches the surface, where the buoyancy force will reduce to equal the weight force (ignoring the slight bobbing the chip will do on the surface).