Download Mechanics

Mechanics Revision
AJC P2 Q2
2
(a) Use Newton’s laws of motion to explain why
an object moving with uniform speed in a
circle must experience a force towards the
centre of the circle.
(b) An aircraft of mass 5.0 × 104 kg moves with
a constant speed of 0.20 km s-1 in a
horizontal circle of radius 15 km.
(i) Show on a sketch the forces acting on
the aircraft in the vertical plane
containing the aircraft and the centre of
the circle.
(ii) Find the magnitude and direction of the
resultant force.
Mechanics Revision
VJC P2 Q2
2
Using a rope, a bucket of water is swung in a
vertical circle of radius 0.950 m. The mass of the
water and bucket is 3.25 kg. At the top of the
circle, the speed of the bucket is 3.23 m s-1 and
the bucket is upside down at this instant.
(a) What is the tension in the rope tied to the
bucket at the top of the circle?
(b) Explain qualitatively why the water in the
bucket does not fall out.
(c) What is the magnitude and direction of the
force acting on the water by the bucket
when it is at the top? Take the mass of
water to be 2.25 kg.
Mechanics Revision
MJC P2 Q1
1
A car, on a steep incline of 37.0° below the
horizontal, rolls down from rest with a constant
acceleration of 4.00 m s-2 along the incline. It
travels 50.0 m down to the edge of a vertical cliff,
which is 30.0 m above the ocean surface as
shown in Fig 1.1.
Find
(a) the speed of the car when it reaches the
edge of the cliff and the time it takes to get
there.
(b) the velocity, v of the car when it lands in the
ocean.
(c) the total time, t that the car takes to move
from point A to C.
Mechanics Revision
RJC P2 Q2
2
When serving a ball, a tennis player first throws
the ball vertically upwards with one hand and hit
the ball at the highest point with his racket in the
other hand.
(a) When the ball is in contact with the racket, a
force of 70 N is exerted on the ball at right
angle to the surface of the racket. The ball
leaves the surface of the racket
perpendicularly with speed 50 m s-1, making
an angle of 8.0° to the horizontal as shown
in Fig 2. below.
(i) Calculate the length of time the ball is in
contact with the racket surface given
that the ball has a mass of 0.060 kg.
(ii) The ball was hit by a racket at the
highest point of its motion which was 3.2
m above the ground. Given that the net
was 1.0 m high and the player was 11.5
m away from the net, how high above
the net was the ball when it passed over
the net? Neglect air resistance.
(b) If the opponent’s reaction is 0.30 s from the
time he sees the player hit the ball and runs
at a speed of 3.0 m s-2 in a straight line
parallel to the vertical plane of the trajectory
of the ball, calculate the distance the
opponent would have run when the ball first
touches his side of the court.