Chapter 3, Motion

Question 1

Defining equation for speed?

Answer 1

v=x/t (speed = change in distance/change in time).

Question 2

Which axis is which on a distance-time graph?

Answer 2

time is x-axis, distance is y-axis.

Question 3

What is given by the gradient of a displacement-time graph?

Answer 3

Velocity.

Question 4

How do you find the instantaneous speed from a distance-time graph?

Answer 4

Draw a tangent.

Question 5

What are the vector quantities of distance and speed?

Answer 5

Displacement and velocity.

Question 6

Defining equation for acceleration?

Answer 6

a=v/t (change in velocity/change in time).

Question 7

How do you find the total displacement from a velocity-time graph?

Answer 7

Find the area under the curve.

Question 8

What do the letters in the suvat equations represent?

Answer 8

s=displacement, u=initial velocity, v=final velocity, a=acceleration, t=time taken.

Question 9

Suvat equation including a,v,u and t?

Answer 9

a=(v-u)/t, derived from defining equation for acceleration

Question 10

Suvat equation including s,u,a and t?

Answer 10

s=ut+(1/2)at^2, from area of trapezium from velocity-time graph. Also s=vt-(1/2)at^2 is also a valid equation.

Question 11

Requirements for suvat equations to apply?

Answer 11

Acceleration is constant for motion in a straight line.

Question 12

Suvat equation including s,u,v and t?

Answer 12

s=(1/2)(u+v)t from the average velocity * time.

Question 13

Suvat equation including s,u,v and a?

Answer 13

v^2=u^2-2as.

Question 14

What factors affect stopping distance?

Answer 14

Thinking distance and breaking distance.

Question 15

How do you calculate thinking distance when stopping a car?

Answer 15

Thinking distance = speed*reaction time

Question 16

What methods are there for determining acceleration due to gravity (g)?

Answer 16

Electromagnet and trapdoor:
An electromagnet holds a steel ball above a trapdoor, when the current is switched off the ball falls breaking the contact in the trapdoor stopping the timer.
Light gates:
Use two sets of double light gates to determine change in velocity
Taking pictures:
By taking pictures of a falling object at small regular intervals you can measure how much more the ball falls each time and use this to measure g.

Question 17

How do you calculate the position of a projectile knowing the initial velocity and angle it was fired at?

Answer 17

Use suvat on the horizontal and vertical components of the velocity separately.