Move your hand in the way indicated by the velocity-time plots below

A car is traveling along a straight road. The first curve on the left represents the car’s position as a function of time.

Which of the other curves best represents the car’s

i) velocity ?

ii) acceleration?

0

x

t

0

0

0c)

b)

a)

t

t

t

0

0e)

d)

t

t

A car on a straight road has the following velocity-time curve

20 40 60 80 100 120

2010 0

-10-20

30

1. Roughly, what is its total displacement in the 120 seconds?

a) 1200m b) 2400m c) 12,000m d) none of the above

2. Which value best represents its acceleration at t=70 s?

a) 1.5 m/s2 b) -1.5 m/s2 c) 0 m/s2

d) 2.0 m/s2 e) -2.0 m/s2

v(t)

xv o

A ball is thrown upwards. If is its

total displacement from the point of

release, when is the equation

valid?

(“Up” is the positive x-

direction)

x

212ox v t a t

(a) Only when the ball is either going up or going down, but not

both.

(b) Over the entire trajectory.

(c) Over the entire trajectory except at the top.

(d) None of the above.

v o 0

v o ?

Can we use the kinematic equations to solve for v if we know the shape of the slide?

A block of wood slides down a frictionless surface as shown below, starting from rest.

212eg ox v t a t

a) Yes, because the surface is frictionless, so the accelerations is 9.80 m/s2 downwards

b) No, because the acceleration is not constant

c) Yes, because the acceleration is constant although not 9.80 m/s2

d) None of the above

The following v(t) graph corresponds to constant acceleration.

v(t)

0

vo

Δt

y mx b Recall:

slope intercept

Which of the equations below is (are) correct?

212

212

a) ( ) b) ( )

c) ( ) ( ) d) ( ) ( )

e) none of the above

o

o

v t a t v at a t

v t v a t v t a t

a 9 8. m s 2

An object is thrown upwards with an initial velocity of 10 m/s.

Which of the following single equations can be used to calculate the time to return to the thrower’s hand?

All are “correct” kinematic equations21

2

212

a) ( ) b) 2

c) ( ) d)

e) all of the above

o

o

v vx v t a t x t

vx v t a t a

t

a = 9.80 m/s2

Slope = a

t

v o

v

Which of the following expressions is the most correct? (why/why not)21

2I) a) b) c) o o ov v a t v v a t v v at

II) a) b) c) 2 2

o oav o av av

v v v vv v v v v

21 12 2

212

III) a) b)

c) d)

o ox v t at x v t at

x vt at x v t

2 2

2 2 2 2

IV) a) 2 b) 2

c) 2 d) 2

o o

o o

v v a t v v a t

v v a v v a x

down

2.0 s

2.4 s

2.8 s

3.2 s

3.6 s

4.0 stime

up

0.8 s

position

0

1.2 s

1.6 s

0.4 s

2.0 s

time

A ball is thrown vertically upwards. The dots below give the positions of it at 0.4s intervals (“up” is the positive direction)

1. What is the ball’s displacement from the start

after 3.2 s? a) –7.1 m b) +12.5 m c) +26.7 m

2. What is the ball’s average velocity between 0.4 s and 3.6 s?

a) b) c) 0 m/s19.6 m 7.1 m

3.2 s

19.6 m 7.1 m

3.2 s

12.5 m 7.1 m

0.4 s

12.5 m 7.1 m

0.4 s

b) 0 m/s

3. What is the ball’s average velocity between 3.2 s and 3.6 s?

a)

c) d) none of the above

19.6 m

18.9 m

16.7 m

12.7 m

7.1 m

0 m

v i

B

A

a b c d e

slope 2 > slope 1slope 1

In the figure above, the circles show the positions of a thrown ball at equal time intervals. represents the initial velocity, just as it leaves the thrower's hand.

(1) Which of the above vectors best represents the instantaneous velocity of the ball at point A?

(2) Which of the above vectors best represents the average velocity of the ball between points A and B?

v i

How do I draw a pictorial/physical representation?How do I know what equation to use?

Jane is driving at 30 m/s when she sees a rabbit on the road ahead. She brakes to a stop in 10 s with a constant deceleration. How far does she go before she stops?

Pictorial:

Physical:

Mathematical: Know: v0 = 30 m/s, v = 0 m/s, Δt = 10 s, Want Δx = ?Formula sheet

v = v0 + a Δt v2 = v0

2 + 2a ΔxΔt

v0

v