Transcript Slide 1

Higher Still Multiple Choice
Mechanics: Forces
1
Which of the following forces is required to lift a
mass of 5 kg vertically upwards near the surface
of the Earth at a constant speed of 4ms-1 ?
20%
A. 5 N
B. 20 N
20%
C. 40 N
20%
D. 50 N
20%
E. 200 N
20%
2
A parachutist of mass 50 kg descends towards
the Earth at a constant velocity of 2 m s -1 .
The upward force acting on the parachutist is
20%
A. 10 N
20%
B. 25 N
C. 100 N
20%
D. 200 N
20%
E. 500 N
20%
3
A block of weight 1500 N is
dragged along a horizontal road
at constant speed by a force of
500N.
What is the force of friction
between the block and the road?
A. 3 N
20%
20%
B. 500 N
20%
C. 1000 N
20%
D. 1500 N
20%
E. 2000 N
4
Force is applied to an object of mass 2 kg,
initially at rest on a friction-free horizontal
surface, as shown in the following force- time
graph.
After 1 second, the speed of the object, in ms-1,
is
20%
A. 7.5
20%
B. 12.5
C. 15
20%
D. 25
20%
E. 30
20%
5
A hot air balloon of mass 300 kg has
people with a total mass of 250 kg on
board. It floats at a steady height.
The upthrust on the balloon is
20%
A. 0 N
20%
B. 500 N
C. 2500 N
20%
D. 3000 N
20%
E. E 5500 N
20%
6
A rocket of mass 1200 kg rises vertically from
a planet which has a gravitational field strength
of 20 N kg-1 . The rocket accelerates away from
the surface of the planet at 2 ms-2.
What force must the rocket motors produce to
give this acceleration?
20%
A. 12 000 N
20%
B. 14 400 N
C. 24 000 N
20%
D. 26 400 N
20%
E. 48 000 N
20%
7
A block X of mass 3 kg is accelerated from rest
by a force of 5 N for 2 s. An identical block Y is
accelerated from rest by a force of 5 N for 4s.
The ratio of kinetic energy of X to kinetic
energy of Y after acceleration is
20%
A. 5 : 3
20%
B. 3 : 4
C. 2 : 1
20%
D. 1 : 2
20%
E. 1 : 4
20%
8
A horizontal force of 40 N is applied to two
wooden blocks of masses 6 kg and 14 kg which
are in contact with each other on a frictionless
horizontal surface as shown.
What is the size of the horizontal force acting
on the 7 kg block?
20%
A. 40 N
20%
B. 28 N
C. 20 N
20%
D. 16 N
20%
E. 12 N
20%
9
Two blocks, X and Y, move along a frictionless
horizontal surface at a constant velocity of 3ms-1.
The force which X exerts on Y is
20%
A. 0 N
20%
B. 1 N
C. 3 N
20%
D. 6 N
20%
E. 9 N
20%
10
A horizontal force of 10 N is applied as
shown to two blocks on a frictionless
horizontal surface.
What force does Y exert on X?
A. 0 N
20%
B. 4 N
20%
20%
C. 5 N
20%
D. 6 N
20%
E. 10 N
11
Two trolleys are joined together by a thread and are
pulled by a horizontal force of 12 N along a level track as
shown. One second after starting from rest, the thread
breaks at X. Neglecting possible effects of friction,
which statements correctly describe the motion of both
trolleys after the thread breaks.
Trolley A
Trolley B
A.
constant velocity of 8ms-1
constant velocity of 4ms-1
20%
20%
B.
uniform acceleration of 4ms-2 uniform acceleration of 4ms-2
20%
C.
uniform acceleration of 12ms-2 constant velocity of 4ms-1
20%
D.
uniform acceleration of 12ms-2 comes to rest
20%
E.
comes to rest
comes to rest
12
A lift is raised and lowered by
means of a cable.
In which of the following
situations is the tension in the
cable greatest?
A. The lift is travelling upwards at constant speed.
20%
B. The lift is travelling downwards at constant speed.
20%
20%
C. The lift is decelerating on the way down.
20%
D. The lift is accelerating on the way down.
20%
E. The lift is decelerating on the way up.
13
An object of mass 1.0 kg hangs from a spring
balance which is suspended on the inside of a
lift. The balance reading is 10 N when the lift
is stationary. What is the reading on the
balance when the lift is accelerating upwards
at 2 m s–2 ? (Use g=10 m s–2 )
A. 2 N
20%
B. 8 N
20%
C. 10 N
20%
D. 12 N
20%
E. 30 N
20%
14
A mass of 0.060 kg is suspended
from a spring balance inside a
lift. The lift accelerates
downwards at 4ms–2 . What is
the reading on the spring
balance during this acceleration?
(Use g=10 m s–2 ).
A. 0.24 N
20%
B. 0.36 N
20%
20%
C. 0.60 N
20%
D. 0.84 N
20%
E. 2.4 N
15
A woman is standing in a lift which is initially at
rest. F is the force which is exerted by the
woman’s feet on the floor of the lift, and R is
the force exerted by the floor of the lift on the
woman’s feet. If the lift begins to accelerate
upwards, what changes, if any, take place in the
magnitudes of F and R?
20%
A. F remains the same; R remains the same.
20%
B. F increases; R remains the same.
C. F remains the same; R increases.
20%
D. F remains the same; R decreases.
20%
E. F increases; R increases.
20%
16
A man is standing in a lift which is initially at rest.
F is the force which is exerted by the man’s feet
on the floor of the lift, and R is the force exerted
by the floor of the lift on the man’s feet. The lift
is initially travelling upwards with a constant
velocity. It then decelerates. When the
deceleration starts what changes, if any, occur in
F and R?
20%
A. F remains the same and R remains the same.
20%
B. F remains the same and R decreases.
C. F remains the same and R increases.
20%
D. F decreases and R decreases.
20%
E. F decreases and R remains the same.
20%
17
A woman weighs 800 N and stands on an
accurate weighing-machine in a lift. The
reading on this weighing-machine is 820 N.
This indicates that the lift is
20%
A. stationary
20%
B. moving upwards at a steady speed.
C. moving downwards at a steady speed.
20%
D. accelerating upwards.
20%
E. accelerating downwards.
20%
18
A mass of 1.0 kg hangs from a
spring balance which is suspended
on the inside of a small rocket.
What will the balance read when
the rocket is accelerating upwards
from the Earth's surface at a
constant rate of 2.0 m s–2 ?
(Use g= 10 m s–2 ).
A. 0 N
20%
20%
B. 2 N
20%
C. 8 N
20%
D. 10 N
20%
E. 12 N
19
Two masses are joined together by
string Y and then hung from a beam
using string X. String X is burned
through using a candle. Neglecting the
mass of each string, what is the
tension in string Y
I Before string X is burned through &
II After string X is burned through?
I Before
20% A. 40 N
20% B. 50 N
20% C. 60 N
20% D. 50 N
20% E. 40 N
II After
40 N
0N
40 N
60 N
0N
20
Two balls, of masses 1kg and 3kg,
joined by a light string as shown,
are falling freely.
Assuming no air resistance, what
is the tension in the string?
20%
A. 0 N
20%
B. 2 N
C. 4 N
20%
D. 10 N
20%
E. 20 N
20%
21
A tension force of 180 N is
applied vertically upwards to a
box of mass 15 kg.
Assuming that the acceleration
due to gravity is 10 m s –2 the
acceleration of the box is
A. 2 m s
20%
–2
B. 8 m s
20%
–2
C. 10 m s
20%
–2
D. 12 m s
20%
–2
E. 20 m s
20%
–2
22