Download exercise 10

Hyndland Secondary
Physics Department
National 5: Dynamics and Space –
Homework Revision Exercises
EXERCISE 1
1. Calculate the average speed of a girl who runs 80m in 10s.
2. Calculate the average speed of a car if it travels 160km in 2hrs.
3. Calculate how far a man running at 8ms-1 will go in 5 minutes.
4. How long will it take a bird, flying at 30kmhr-1 to go 210km?
5. A trolley with a 5cm mask is allowed to roll down a slope between two light
gates, 1m apart, as shown.
light gate 1
5cm
light gate 2
1m
..
The following results were obtained:
Time for mask to pass through light gate 1 = 0.40s.
Time for mask to pass through light gate 2 = 0.08s.
Time for trolley to travel from light gate 1 to light gate 2 = 2.5s.
Find (a) the average speed of the trolley down the slope.
(b) the instantaneous speed of the trolley at the bottom of the slope.
6. A motorbike ‘wheelie’ means riding on the back wheel only. The record for
a ‘wheelie’ is 331 000 m non-stop.
(a) Calculate the average speed of the motorbike if the distance was
covered in 6 000 seconds.
(b) Describe how the average speed of the motorbike could be measured.
The fastest speed ever recorded for a motorbike was over 512 km/h. This
record was set by Donald A. Vesco in 1978 on a bike with two engines.
(c) Suggest how this instantaneous speed could have been measured.
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EXERCISE 2 - acceleration
1. Calculate the acceleration of a car which takes 8s to increase its speed
from 20ms-1 to 30ms-1.
2. Find the acceleration of a sprinter who reaches a speed of 8ms -1 after 2s
of a race.
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4. A gun fires a bullet at 600ms-1. If it leaves the gun barrel 15ms after the
trigger is pulled, find the acceleration of the bullet.
5. A lorry travelling at 30ms-1 takes 6s to come to a halt after the brakes are
applied. Find its deceleration.
6. A jet plane moving at 450ms-1 accelerates at 18ms-2 for 7s. Calculate the
final speed of the plane.
7. A driver presses the accelerator for 5s and reaches a speed of 30ms -1. If
her acceleration was constant at 2ms-2. Calculate her initial speed.
8. During the Winter Olympics two skiing competitions are taking place. Both
downhill racing and ski jumping are fast and dangerous sports which are
very popular with spectators.
Blake : 2 mins 33·21 s
In down hill racing an electric clock automatically starts when the skier
opens the start gate. The time for one competitor to complete a 3 km race
is shown above.
(a) Calculate the average speed of the skier during this race.
At the finish line of the race a light gate is arranged so that the
instantaneous speed of the skier can be measured.
(b) Using the information below calculate the final speed of the skier.
width of skier when crouched down (average ) = 60 cm
time on electronic clock = 0·02 s
(c)
Calculate the acceleration of the skier during the race.
EXERCISE 3- acceleration from v-t graph
1. The graph below shows how the speed of an object varies with time.
v
E
B
F
C
D
A
Which parts of the graph show (a) constant speed
(b) speeding up
(c) slowing down?
2
G
t
3. The graph below shows part of the journey of a car as it leaves the traffic
lights.
10
speed in
m/s
8
6
4
2
5
10
15
20
25
30
time in seconds
35
40
Use the graph to
(a) Describe the motion of the vehicle during the first 25 seconds of its
journey.
(b) Calculate the acceleration during the first 10 seconds of the journey.
EXERCISE 4- distance from v-t graph
1.
2.
EXERCISE 5- mass and weight
1.
Calculate the weight of a girl who has a mass of 40kg.
2.
What is the gravitational force acting on a 30g rock on the Earth’s
surface?
3.
Find the mass of a boy who weighs 550N.
5.
An astronaut on the Moon uses a newton balance to measure the
weight of a 20kg rock. If the reading on the balance is 32N, calculate
the gravitational field strength on the Moon.
6.
The gravitational field strength on Venus is 8.8Nkg-1. If a robot probe of
mass 270kg lands on Venus, how much will it weigh?
4.
7.
If a man weighs 700N on Earth, how much would he weigh on Jupiter
which has a gravitational field strength of 26Nkg-1?
EXERCISE 6 – Newton’s Laws
1.
Find the unbalanced force required to accelerate a 6kg mass at 3ms-2.
2.
Find the acceleration of a 200kg rock, rolling down a hill, if the
unbalanced force acting on it is 1kN.
3.
What is the mass of a trolley if an unbalanced force of 12N causes it to
accelerate at 4ms-2?
4.
The forces acting on a car of mass 1000kg are shown below.
Friction
2kN
(a) Find the unbalanced force acting on the car.
(b) Calculate the acceleration of the car.
5
6kN
Engine force
6.
Stephen and Jack are invited along to ‘Techno toys’ workshop to try
out a new remote control car. They line the car up to race along the 200 m
track and then start it off.
(a)
Describe how the designers could work out the car’s
instantaneous speed as it goes round the corner of the track. Your answer
must include:
any apparatus they would need
any measurements they would take
any calculations they would do.
The speed time graph below represents the motion of the car during
part of the race.
speed
in m/s
10
9
8
7
6
5
4
3
2
1
0
2
4
6
8
10
12
14
16
18
20
22
24 time in seconds
(b)
Calculate the acceleration of the car during the first 6 seconds.
(c)
How far did the car travel during the 18 seconds represented by
the graph.
(d)
During the period 6 s to 14 s the car exerted an engine force of
450 N. What size are the frictional forces acting on the car at
this time.
(e)
How could the designers reduce the frictional forces acting on
the car.
(f)
Draw the graph that would have been produced if the race had
taken place on a wet day.
EXERCISE 7
1
(i)
Calculate the unbalanced force
acting on the spacecraft.
(ii)
Find the mass of the spacecraft.
(iii)
Calculate the initial acceleration.
2. Cosmologists use “light years” as a unit of distance.
(a) Calculate the number of metres in 1 light year.
(b) The Leo A Galaxy is 2.25 million light years from the Earth.
Calculate this distance in metres.
3. The nearest star to our solar system is Proxima Centauri which is 3·99
x1016 m away. How far is this in light years?
4. The Sun is the nearest star to the planet Earth. It takes light 8·3 minutes to
reach us from the Sun. Use this information to find out the distance from the
Earth to the Sun in kilometres.
5. Sir William Herschel, an amateur astronomer, discovered the planet Uranus
in March 1781. Uranus is 2 871 x 106 km away from the sun. How long does
it take for sunlight to reach Uranus?
EXERCISE 8
1. We now have evidence to support the Big Bang Theory.
a. State two pieces of evidence that scientists have provided that
support the Big Bang Theory.
b. Provide a description of how each piece of evidence supports
ideas in the Big Bang Theory.
2. Various technologies that were originally developed in space
exploration programmes has proved to be useful in everyday life.
a. Write down one technology that was originally developed for a
space programme that is now used in everyday life.
b. Describe briefly how the technology benefits society.
3. An astronomer views the following objects in the night sky:
Jupiter, which orbits the Sun;
Europa, which orbits Jupiter;
The Andromeda Galaxy.
a. Which of the objects mentioned is a moon?
b. Which of the objects mentioned is a planet?
c. Which of the objects mentioned is a star?
4. Scientists searching for exoplanets use the Astronomical Unit. 1 A.U.
is the distance from the Sun to Earth.
The “Habitable Zone” is the range of distances from a star which could
be suitable for a planet to support life.
If a planet is orbiting a star which is twice as luminous (bright) as the
Sun:
a. Provide an estimate of the distance that the planet would have
to be from the star in Astronomical Units.
b. Give a reason for your answer.
EXERCISE 9
Scalars and Vectors
1. Physical quantities can be categorised as either scalar or vector.
a. Describe what is meant by a scalar quantity.
b. Describe what is meant by a vector quantity.
c. Sort the following into a table with the headings scalar quantity
and vector quantity.
force
distance
displacement
velocity
speed
time
2. During a race, a car makes 25 complete laps of a course of 5 km.
a. What is the total distance travelled by the car after 25 complete
laps?
b. What is the resultant displacement of the car after 25 complete
laps?
3. An athlete runs 8 km due west then turns and runs 6 km due north as
shown in the diagram.
000˚
FINISH
270˚
6 km
090˚
180˚
8 km
START
a. What is the total distance that the athlete travelled?
b. By scale diagram or otherwise, find the resultant displacement
of the athlete.
c. The run was completed in 75 minutes.
i. Calculate the average speed of the athlete in km/h.
ii. Calculate the average velocity of the athlete in km/h.
EXERCISE 10
1. Josie and Kirsty are arguing about how a water rocket water lifts off.
Josie
Kirsty
Dave
Dave knows that what Josie says isn’t true, but Kirsty has not provided
an actual explanation either.
Dave reminds Kirsty about Newton’s Third Law and they both go back
and offer an explanation to Josie.
Copy and complete what they say to Josie.
“OK Josie, this is to do with Newton’s Third Law. The rocket pushes the
water _ _ _ _ _ _ _ _ _ and the _ _ _ _ _ pushes the rocket _ _ _ _ _ _ _
with an _ _ _ _ _ sized force “. It has nothing to do with the _ _ _ _ _
pushing on the ground.
2. Show how gravitational field strength and acceleration due to gravity
are equivalent.
3. A student drops a football from above her head.
It lands on the ground 0.63 seconds after being dropped.
Calculate the velocity of the ball at the instant it strikes the ground.
Assume that air resistance is negligible.
4. An astronaut drops a hammer on the Moon where the gravitational field
strength is 1.6 N/kg.
The hammer lands on the surface of the Moon 2.1 seconds after being
dropped.
a. Show that the hammer strikes the surface of the Moon with a
velocity of 3.36 m/s.
b. Draw a velocity-time graph for the hammer as it falls.
Use the graph to calculate the height that the hammer was dropped from.
EXERCISE 11
Projectile Motion
1. A javelin is launched horizontally at 5 m/s. It lands 15 metres
horizontally from its launch point.
5 m/s
15 metres
a. Calculate the time that the javelin is in the air for.
b. Calculate the final vertical velocity of the javelin.
Using a scale diagram or otherwise, find the size of the final resultant
velocity of the javelin and the angle of impact.
2. A ball rolls off a table top with a horizontal speed of 2.0 m/s.
The ball hits the ground 0.3 seconds later.
a. Calculate the horizontal distance that the ball lands from the
table top.
b. Calculate the final vertical speed of the ball.
c. Sketch a velocity-time graph of the vertical motion of the ball.
d. Use the graph to find the height of the table.
3. Explain how an artificial satellite such as the International Space
Station remains in orbit around the Earth.
EXERCISE 12
1. Calculate the work done when a force of 50N is used to move an object a
distance of 20m.
50N
NN
N
20m
2. Find the work done when a 2N force moves an object 50cm.
3. How much energy is converted when a 5kN force is used to move an object
0.5km?
4. A winch uses an average force of 700N to lift an injured climber 40m up
into a mountain rescue helicopter. Calculate the work done.
5. Find the force used when 200J of work is done moving an object 8m.
6. If an ant does 78mJ of work while dragging a leaf a distance of 130mm, find
the average force used.
7. If 1.2kJ of work is done in pushing a filing cabinet 4m across a floor, find
the average force used.
8. If a force of 60N is used to push a vacuum cleaner until 720J of work has
been done. What distance has it moved?
9. When a toy car is wound up it stores 100J of energy. If it travels across a
floor at a constant speed, and the frictional force acting is 12.5N, find how far
it can go before running out of energy.
10. When fully charged, the battery of a forklift truck stores 20MJ of energy.
Calculate how far it can carry a load that requires an engine force of 5kN.
11.
EXERCISE 13
(g = 9.8Nkg-1)
1. Calculate the potential energy gained by a 10kg mass when it is raised to a
height of 10m.
2. A football of mass 600g is kicked 12m up into the air. How much potential
energy does it gain?
3. A diver of mass 60kg dives from a platform 5m up. Find how much potential
energy she loses.
4. A man of mass 80kg uses a lift to go from the second floor of a building (6m
above ground level), up to the eighth floor (24m above ground level).
Calculate the change in potential energy.
5. An astronaut on the Moon throws a stone of mass 2kg to a height of 25m. If
the gravitational field strength on the Moon is 1.6Nkg-1, find the potential
energy gained.
6. A dog of mass 20kg gains 784J of potential energy by climbing up a flight
of stairs. Calculate the height of the stairs.
7. A rock of mass 4kg falls from the top of a cliff and loses 4.9kJ of potential
energy. How high is the cliff?
8. During the high jump event in the school sports a girl just clears the bar at a
height of 1.25m. If she has 490J of potential energy at this height, what is her
mass?
9. A pencil rolls off a desk 80cm high and has lost 196mJ of potential energy
by the time it reaches the floor. Find the mass of the pencil.
10. An alien on the surface of Jupiter has a mass of 200kg. If it gains 5.2MJ of
potential energy by rising to a height of 1km above the surface, calculate the
gravitational field strength on Jupiter.
EXERCISE 14
1. Calculate the kinetic energy of a 2kg mass moving at 2ms-1.
2. Calculate the kinetic energy of a sprinter of mass 80kg running at 10ms -1.
3. Find the kinetic energy of a horse of mass 600kg running at 15ms-1.
4. How much kinetic energy will a car of mass 1200kg have when it is
travelling at 30ms-1?
5. Calculate the kinetic energy of a fly of mass 1g moving at 1ms-1.
6. If an object travelling at 5ms-1 has 100J of kinetic energy, calculate its
mass.
7. The bus below has 1.2MJ of kinetic energy.
20ms-1
What is the mass of the bus?
8. The cyclist below has a mass of 80kg.
What speed must he move at in order to have 9kJ of kinetic energy?
9.
EXERCISE 15
(g = 9.8Nkg-1)
1. A ball of mass 1kg is thrown upwards at 10ms-1.
(a) Calculate the initial kinetic energy of the ball.
(b) How much potential energy does the ball have at its highest point?
(c) Find the maximum height reached.
2. A slate of mass 2kg falls off a roof 45m up.
(a) Calculate the potential energy lost.
(b) Find the speed of the slate on impact.
3. A motorbike has 40kJ of kinetic energy at the moment the brakes are
applied.
(a) If it takes 125m to come to a stop, find the average frictional force
acting.
(b) Where has the kinetic energy gone?
4. A skier of mass 50kg starts from rest at the top of a slope and is moving at
20ms-1 by the time she reaches the bottom.
40m
100m
(a) Calculate her potential energy at the top of the slope.
(b) Calculate her kinetic energy at the bottom of the slope.
(c) Find the energy lost as heat due to friction.
(d) Calculate the average value of the frictional force.
5.
EXERCISE 16
1. White light is part of the electromagnetic spectrum – a family of radiation
waves with different wavelengths.
a. List all of the members of the electromagnetic spectrum, from
shortest wavelength to longest wavelength.
b. What property do all of the members have in common?
c. White light can be split into different colours.
X
Y
Z
i. Which of the colours blue, green and red are seen at each
position X, Y and Z?
ii. The same device can be used to analyse light from a star.
iii. What information can be obtained from this analysis?