A basketball of mass $0.625 \mathrm{kg}$ is thrown from a height of $2 \mathrm{m}$ with a speed of $6 \mathrm{m}{ \mathrm{s}}^{-1}$. It passes through the hoop at a height of $3 \mathrm{m}$ with speed $4 \mathrm{m}{ \mathrm{s}}^{-1}$.

Find the change in the kinetic energy of the ball, stating whether this is an increase or a decrease.

A basketball of mass $0.625 \mathrm{kg}$ is thrown from a height of $2 \mathrm{m}$ with a speed of $6 \mathrm{m}{ \mathrm{s}}^{-1}$. It passes through the hoop at a height of $3 \mathrm{m}$ with speed $4 \mathrm{m}{ \mathrm{s}}^{-1}$.

Find the change in the potential energy of the ball, stating whether this is an increase or a decrease.

A basketball of mass $0.625 \mathrm{kg}$ is thrown from a height of $2 \mathrm{m}$ with a speed of $6 \mathrm{m}{ \mathrm{s}}^{-1}$. It passes through the hoop at a height of $3 \mathrm{m}$ with speed $4 \mathrm{m}{ \mathrm{s}}^{-1}$.

What difference does changing the ball's angle of projection make?

A lorry of mass $16000 \mathrm{kg}$ moves on a straight hill inclined at angle $\alpha °$ to the horizontal. The length of the hill is $500 \mathrm{m}$.

While the lorry moves from the bottom to the top of the hill at constant speed, the resisting force acting on the lorry is $800 \mathrm{N}$ and the work done by the driving force is $2800 \mathrm{kJ}$. Find the value of $\alpha$.

A lorry of mass $16000 \mathrm{kg}$ moves on a straight hill inclined at angle $\alpha °$ to the horizontal. The length of the hill is $500 \mathrm{m}$.

On the return journey the speed of the lorry is $20 \mathrm{m}{ \mathrm{s}}^{-1}$ at the top of the hill. While the lorry travels down the hill, the work done by the driving force is $2400 \mathrm{kJ}$ and the work done against the resistance to motion is $800 \mathrm{kJ}$. Find the speed of the lorry at the bottom of the hill.

A box of mass $20 \mathrm{kg}$ moves across a horizontal floor. The coefficient of friction between the box and the floor is $0.2$, and friction is the only resistance force. The box has initial speed $3 \mathrm{m}{ \mathrm{s}}^{-1}$ and moves until it comes to rest.

Find the retardation (negative acceleration) of the box.

A box of mass $20 \mathrm{kg}$ moves across a horizontal floor. The coefficient of friction between the box and the floor is $0.2$, and friction is the only resistance force. The box has initial speed $3 \mathrm{m}{ \mathrm{s}}^{-1}$ and moves until it comes to rest.

Find the distance that the box travels.

A box of mass $20 \mathrm{kg}$ moves across a horizontal floor. The coefficient of friction between the box and the floor is $0.2$, and friction is the only resistance force. The box has initial speed $3 \mathrm{m}{ \mathrm{s}}^{-1}$ and moves until it comes to rest.

Find the work done against friction.

Sam and his skateboard have a combined mass of $100 \mathrm{kg}$. He accelerates from $0 \mathrm{m}{ \mathrm{s}}^{-1}$ to $20 \mathrm{m}{ \mathrm{s}}^{-1}$ while descending a hill. The hill is modelled as a slope at an angle of ${\sin }^{-1}0.2$ to the horizontal. The non-gravitational resistance is $200 \mathrm{N}$. The bottom of the hill is $10 \mathrm{m}$ below the top of the hill. Find the increase in the kinetic energy of Sam and his skateboard. (Use $g=10 \mathrm{m} {\mathrm{s}}^{-2}$)