Chapter 3 - motion and SUVAT

Question 1

formula of average speed

Answer 1

average speed = total distance/total time

Question 2

key points of a distance time graph

Answer 2

• distance on Y
• time on x
• speed is gradient
• acceleration = increasing gradient
• for instantaneous speed draw a tangent

Question 3

difference between a vector and a scalar

Answer 3

a vector has a magnitude and direction

a scalar has only a magnitude

Question 4

equation for velocity

Answer 4

velocity = displacement/time

Question 5

displacement- time graphs

Answer 5

very similar to distance time graphs but gradient is now velocity

Question 6

definition of acceleration and equation for acceleration

Answer 6

equation is the rate in change of velocity

acceleration = change in velocity/time

Question 7

velocity-time graph key points

Answer 7

• gradient = acceleration
• can be +ve or -ve
• area under graph is displacement

Question 8

SUVAT equation without s

Answer 8

v = u + at

Question 9

SUVAT equation without a

Answer 9

s = ((u+v)/2 ) x t

Question 10

SUVAT equation without t

Answer 10

v^2 = u^2 + 2as

Question 11

SUVAT equation without u

Answer 11

s = vt - 1/2at^2

Question 12

SUVAT equation without v

Answer 12

s = ut + 1/2at^2

Question 13

what are the components of stopping distance

Answer 13

stopping distance = thinking distance + braking distance

Question 14

what is thinking distance

Answer 14

thinking distance is the distance traveled during the driver’s reaction time given by
thinking distance = speed x reaction time

Question 15

calculating braking distance

Answer 15

suvat can be used to calculate this

B.D. is proportional to V^2

Question 16

what is meant by an object in free fall

Answer 16

it is accelerating under gravity = 9.81ms^-2

Question 17

explain the method of determining G using an electromagnet and a trap door

Answer 17

• an electromagnet holds a small steel ball
• when the current is switched off, the ball drops and a timer starts
• the ball falls and hits a flap which stops the timer
• using SUVAT s = 1/2at^2
• this is because our U is 0

Question 18

explain how the determination of G experiment can be improved using light gates

Answer 18

• The electromagnet and trapdoor may cause delays in the timing
• light gates can be used instead

Question 19

explain the method of determining G using photos

Answer 19

• a small metal ball is dropped next to a metre rule
• its fall is recorded or photos taken
• the ball’s position at different time period can be used to calculate G by using cumulative distance and time
• plot s against t^2, u = 0 thus gradient = 1/2 g

Question 20

calculating G graphically

Answer 20

plot s against t^2 and the gradient = G/2

Question 21

what is the key fact when considering projectile motion

Answer 21

“in projectile motion the horizontal and vertical components are independent of each other”

Question 22

assuming no air resistance, what can we say about projectile motion

Answer 22

• vertical component only changes due to G
• vertical motion uses SUVAT
• horizontal velocity remains constant and uses d = s x t

Question 23

vector calculations explained

Answer 23

at any point (if you know the time) the vectors of an object in projectile motion can be calculated, thus the angle can be calculated.

Question 24

what is a projectile

Answer 24

an object acted upon only by the force of gravity

Question 25

what is meant by a constant velocity

Answer 25

speed and direction of motion do not change

Question 26

if an object in water is moving vertically down, what 3 forces are acting on it, thus how does the resultant force change from the object being submerged to reaching its deepest point

Answer 26

upthrust, weight and friction

• resultant force decreases as depth increases because speed decreases so the upwards acting drag force decreases, hence the magnitude of the resultant force decreases