Jan Dangerfield, Stuart Haring and, Julian Gilbey Solutions for Exercise 4: EXERCISE 2C

A feather of mass $10 \mathrm{g}$ falls from rest from a height of $3 \mathrm{m}$ and takes $2 \mathrm{s}$ to hit the ground. Find the air resistance on the feather.

A ball of mass $0.3 \mathrm{kg}$ is thrown upwards with speed $10 \mathrm{m}{ \mathrm{s}}^{-1}.$ It experiences air resistance of $0.15 \mathrm{N}.$ The ball lands on the ground $1.2 \mathrm{m}$ below. Find the speed with which it hits the ground.

A bouncy ball is dropped from a height of $5 \mathrm{m}.$ When it bounces its speed immediately after impact is $80\%$ of the speed immediately before impact.

Find the maximum height of the ball after bouncing.

A bouncy ball is dropped from a height of $5 \mathrm{m}.$ When it bounces its speed immediately after impact is $80\%$ of the speed immediately before impact.

Show that the height is independent of the value used for $g.$

A parachutist of mass $70 \mathrm{kg}$ falls out of an aeroplane from a height of $2000 \mathrm{m}$ and falls under gravity until $600 \mathrm{m}$ from the ground when he opens his parachute. The parachute provides a resistance of $2330 \mathrm{N}.$ Find the speed at which the parachutist is travelling when he reaches the ground.

A ball is thrown vertically up at $10 \mathrm{m}{ \mathrm{s}}^{-1}.$ One second later another ball is thrown vertically up from the same point at $8 \mathrm{m}{ \mathrm{s}}^{-1}.$ Find the height at which the balls collide.

A pebble is dropped from rest into a deep well. At time $t s$ later it splashes into the water at the bottom of the well. Sound travels at $340 \mathrm{m}{ \mathrm{s}}^{-1}$ and is heard at the top of the well $5 \mathrm{s}$ after the pebble was released. Find the depth of the well.

A ball of mass $2 \mathrm{kg}$ is projected up in the air from ground level with speed $20 \mathrm{m}{ \mathrm{s}}^{-1}.$ It experiences constant air resistance $R.$ It returns to ground level with speed $15 \mathrm{m}{ \mathrm{s}}^{-1}.$ Find $R.$