Use the definition of displacement to explain how it is possible for an athlete to run round a track yet have no displacement.

A girl is riding a bicycle at a constant velocity of $3.0 m{s}^{-1 }$ along a straight road. At time time $\mathrm{t}=0$, she passes her brother sitting on a stationary cycle. At time $t=0$, the boy sets off to catch up with his sister. His velocity increases from time $\mathrm{t}=0$ until $\mathrm{t}=5 \sec .$when he overed a distance of $10 \mathrm{m}$. He then continues at a constant velocity of $4.0 {\mathrm{ms}}^{-1}$.

Draw the displacement tome graph for the girl from time $\mathrm{t}=0 \mathrm{to} \mathrm{t}=12 \sec .$ 

A girl is riding a bicycle at a constant velocity of $3.0 m{s}^{-1 }$ along a straight road. At time time $\mathrm{t}=0$, she passes her brother sitting on a stationary cycle. At time $t=0$, the boy sets off to catch up with his sister. His velocity increases from time $\mathrm{t}=0$ until $\mathrm{t}=5 \sec .$when he overed a distance of $10 \mathrm{m}$. He then continues at a constant velocity of $4.0 {\mathrm{ms}}^{-1}$.

Draw the displacement tome graph for the girl from time $\mathrm{t}=0 \mathrm{to} \mathrm{t}=12 \sec .$ 

 On the same graph draw the graph for the boy

A girl is riding a bicycle at a constant velocity of $3.0 m{s}^{-1 }$ along a straight road. At time time $\mathrm{t}=0$, she passes her brother sitting on a stationary cycle. At time $t=0$, the boy sets off to catch up with his sister. His velocity increases from time $\mathrm{t}=0$ until $\mathrm{t}=5 \sec .$when he overed a distance of $10 \mathrm{m}$. He then continues at a constant velocity of $4.0 {\mathrm{ms}}^{-1}$.

Draw the displacement tome graph for the girl from time $\mathrm{t}=0 \mathrm{to} \mathrm{t}=12 \sec .$ 

 On the same graph draw the graph for the boy

 Using your graph, determine the value of $\mathrm{t}$ when the boy catches up with his sister.

A student drops a small black sphere alongside a vertical scale marked in centimetres. A number of flash photographs of the sphere are taken at $0.1 sec.$ intervals, The diagram is shown sideways-the first black dot is a $0 cm.$ and the next at $4.0 \mathrm{cm}$

. The first photograph is taken with the sphere at the top, at the time $t=0 sec.$.

Explain how the figure shows that the sphere reaches a constant speed

A student drops a small black sphere alongside a vertical scale

A student drops a small black sphere alongside a vertical scale marked in centimetres. A number of flash photographs of the sphere are taken at $0.1 \sec .$intervals, The diagram is shown sideways-the first black dot is a $0 cm.$and the next at $4.0 \mathrm{cm}$

. The first photograph is taken with the sphere at the top at the time $t=0 sec.$.

 Determine the constant speed reached by the sphere.

 

A student drops a small black sphere alongside a vertical scale

A student drops a small black sphere alongside a vertical scale marked in centimetres. A number of flash photographs of the sphere are taken at $0.1 \mathrm{s}$intervals,The diagram is shown sideways-the first black dot is a $0 cm.$and the next at $4.0 \mathrm{cm}$.The first photograph is taken with the sphere at the top at the time $t=0 sec.$.

 Determine the distance that the sphere has fallen when $\mathrm{t}= 0.8 \mathrm{s}$
 

A student drops a small black sphere alongside a vertical scale

A student drops a small black sphere alongside a vertical scale marked in centimetres. A number of flash photographs of the sphere are taken at $0.1 \mathrm{s}$intervals,The diagram is shown sideways-the first black dot is a $0 cm.$and the next at $4.0 \mathrm{cm}$.The first photograph is taken with the sphere at the top at the time $t=0 sec.$.

In a real photograph, each image of the sphere appears slightly blurred, because each flash is not instantaneous and takes a time of $0.0010 \mathrm{s}$. Determine the absolute uncertainty that this gives in a position of the black sphere when it is travelling at a final constant speed.

 Suggest whether this should be observable on the diagram.