Download Forces Test Year 11

Forces Test Year 11
1 The net force on the following object is
2N
2N
2N
(a) 1N to the right
3N
(b) 1N to the left
(c) 9N
(d) 5N
2 Which of the following objects has no net force on it?
(a) A car accelerating at 2ms-2
(b) a car going round a corner at a constant speed of 1.2 ms-1
(c) A car rolling with the engine off coming to a gradual stop.
(d) a car rolling down a hill at a constant speed of 2ms-1
3 In deep space an astronaut on a space walk needs a jet pack with at least four
little jets. The jet A for example thrusts fuel downwards and this pushed the
astronaut upwards. The force provided by these jets is about 20N
If the astronaut has a mass of 120kg and is moving downward at 3ms-1 (relative to
her ship) which jet needs to be fired and for how many seconds must it fire to bring
the astronaut back to the same speed as the space ship.
(a) Jet A 18 seconds
(b) Jet B, 18 seconds
(c) Jet A, 0.05 seconds
(d) Jet B, 0.05seconds
4 The jet A will not push the astronaut up in the air if the astronaut is standing on
the earth because
(a) The air prevents the fuel from coming out of the jets.
(b) The air creates too much friction
(c) The jets are not strong enough to overcome the force of gravity on the earth
(d) The astronaut has greater mass on the earth.
5 a bullet of mass 1x10-2 kg is fired into a fixed wooden block
At time t=0 it enters the block at P and is brought to rest at R
P
R
d
The graph represents the velocity time relation for the bullet after it enters the
block.
Velocity (ms-1 )
300
0.003
t (s)
Which of the following graphs best represents the relation between the magnitude
of the force of the block on the bullet and time?
F
F
t
F
F
t
t
t
7 A skier comes down a slope and glides along a horizontal section of ground at a
constant speed. The mass of the skier and all his gear is 120 kg
(a) Draw in the vectors to show all the forces acting on the skier in the situation
above. Give magnitude to each of the vectors. State clearly what each force is.
(b) In another colour state the reaction pair to the forces you have already drawn.
8 A force of 5.2 N acts on a body at rest on a smooth horizontal surface and causes
the mass to have an acceleration of 1.3 ms-2 to the right
(a) What is the mass of the body?
(b) After the body has been moving along the smooth surface for a time it reaches
a rough surface for which the force of friction is 2.2 N. What is the acceleration of
the mass along the rough surface?
9 Look at the graph below carefully. A student pulls a cart with a spring balance
with various forces. and measures the acceleration of the cart. This is the graph she
put in her results.
Find the slope of this graph.
**Using the 2nd Law state the relationship between the mass of the cart and the
slope of the line
**What does the x intercept on the graph tell us about the experiment?
10 A man with a mass of 100kg is standing in a lift as shown below. He normally
weighs 9800N but on the scales in the lift he weighs 7800N
Draw in the forces on the man.
Calculate the acceleration of the lift.
Is it possible for the man to apparently double his weight in this lift? Explain your
answer.
11 Jane is a naughty girl and going around the ice rink trying to push over various
stationary skaters as shown.
(a) Which of the skaters will accelerate the most after a shove from Jane? Justify
your answer.
(b) Assume all the skaters get the same size push from Jane and that Jane is
stationary when she pushes each of them. In which situation above will Jane get
the greatest acceleration? Explain your answer.
(c) Jane and Tom are the same size. Jane skates at 2.0 ms-1 into stationary Tom and
holds on to him. What is the speed of the couple after they join?
12 A stationary cannon of mass 1400kg fires a cannon ball of mass 4kg. find the
recoil velocity of the cannon. (Ignore friction)
13
9 A truck is traveling with a trailer as shown. The mass of the trailer is 580 kg the
mass of the truck is 1500kg The truck has a thrust of 10 400N
(a) Neglecting friction find the acceleration of the car and trailer
(b) Calculate the tension in the cable between the car and trailer
(c) If the cable suddenly snaps describe what will happen to the velocity of the
trailer (assume no friction)
Justify your answer in terms of Newton’s laws.
(d) Predict what will initially happen to the velocity of the car.