Supplemental Questions 12U
Motion and Forces – Questions
The fastest of all fishes is the sailfish. If a sailfish accelerates at a rate of 14 (km/hr)/sec [fwd] for 4.7 s from
its initial velocity of 42 km/h [fwd], what is its final velocity?
An arrow strikes a target in an archery tournament. The arrow undergoes an average acceleration of 1.37
x103 m/s/s [W] in 3.12 x 10-2 s, the stops. Determine the velocity of the arrow when it hits the target.
A baseball travelling horizontally at 41 m/s [S] is hit by a baseball bat, causing its velocity to become 47 m/s
[N]. The ball is in contact with the bat for 1.9 ms, and undergoes constant acceleration during this interval.
What is that acceleration?
A steel ball is thrown from the ledge of a tower so that it has an initial velocity of magnitude 15.0 m/s. The
ledge is 15.0 m above the ground. Air resistance is negligible.
a. What are the total flight time and the speed of impact at the ground if the initial velocity is
downward?
A baseball pitcher throws a ball vertically upward and catches it at the same level 4.2 s later.
a. With what velocity did the pitcher throw the ball?
b. How high does the ball rise?
A hot air balloon is moving with a velocity of 2.1 m/s [up] when the balloonist drops a ballast (a large mass
used for height control) over the edge. The ballast hits the ground 3.8 s later.
Determine the constant acceleration needed for a bullet to reach a muzzle velocity of 4.0 x 10 2 m/s [fwd],
provided friction is zero and the muzzle is 0.80 m long.
A helicopter travelling horizontally at 155 km/h [E] executes a gradual turn, and after 56.5 s flies at 118
km/h [S]. What is the helicopter’s average acceleration in kilometres per hour per second?
A pilot is required to fly directly from London, UK, to Rome, Italy in 3.5 h. The displacement is 1.4 x 10 3
km [43 E of S]. A wind is blowing with a velocity of 75 km/h [E]. Determine the required velocity of the
plane relative to the air.
Determine the net force on objects E, F, and G.
a. At a particular instant, a soaring bird (E) is subject to an upward lift of 3.74 N, a downward
gravitational force of 3.27 N, and a horizontal air resistance force of 0.354 N.
A boy pushes a lawn mower (m=17.0 kg) starting from rest across a horizontal lawn by applying a force of
32.9 N straight along the handle, which is inclined at an angle of 35.1 above the horizontal. The magnitude
of the mower’s acceleration is 1.37 m/s2, which lasts for 0.58 s, after which the mower moves at a constant
velocity. Determine the magnitude of
a. the normal force on the mower
b. the frictional force on the mower
c. the maximum velocity of the mower
d. the force applied by the boy needed to maintain the constant velocity
Blocks X and Y, of masses mx= 5.12 kg and my= 3.22 kg, are connected by a fishing line passing over an
essentially frictionless pulley (Figure 12).
a. Show that block X slides up the incline wit a positive acceleration. Determine the magnitude of that
acceleration. Friction is negligible.
b. Determine the magnitude of the tension in the fishing line.
Mercury orbits the Sun in an approximately circular path, at an average distance of 5.79 x 10 10 m, with a centripetal
acceleration of magnitude 4.0 x 10-2 m/s2. What is its period of revolution around the Sun in seconds?
A bird of mass 0.211 kg pulls out of a dive, the bottom, of which can be considered to be a circular arc with the radius
of 25.6 m. At the bottom of the arc, the bird’s speed is a constant 21.7 m/s. Determine the magnitude of the upward lift
on the bird’s wings at the bottom of the arc.
At a certain point between Earth and the Moon, the net gravitational force exerted on an object by Earth and the Moon
is zero. The Earth-Moon centre-to-centre separation is 3.84 x 105 km. The mass of the Moon is 1.2% the mass of
Earth.
a. Where is this point located? Are there any other such points? (Apply the quadratic formula after setting up the
related equations.)
b. What is the physical meaning of the root of the quadratic equation whose value exceeds the Earth-Moon
distance? (An FBD of the object in this circumstance will enhance your answer.)