Problems in Aplications of Newton's Laws part 1 (Soal-Soal Aplikasi Hukum Newton Bagian ke-1)

Soal-Soal Aplikasi Hukum Newton  Bagian ke-1

1. Caught without a map again, Hayley lands her  spacecraft on an unknown planet.
Visibility is poor,but she finds someone on a local communications channel and asks
for directions to Earth. "You're already on Earth," is the reply, "Wait there and I'll be
right over." Hayley is suspicious, however, so she drops a lead ball of mass 76.5 g
from the top of her ship, 18 m above the surface of the planet. It takes 2.5 s to
reach the ground.
(a) If Hayley's mass is 68.5 kg, what is her weight on this planet?
( b) Is she on Earth?

2. Dean reads in his physics book that when two people pull on the end of a rope in
a tug-of-war, the forces exerted by each on the other are equal and  opposite, according
to Newton's third law. Misunderstanding the law tragically, Dean runs out to
challenge Hugo the Large, convinced that the laws of physics guarantee a tie. Hugo
lumbers over, picks up  the rope, pulls Dean off his feet, and then drags him

through a puddle, across the road, and up the steps of  the physics building. Use
a force diagram to show Dean that, in spite of Newton's third law, it is possible 
for one side to win a tug-of-war.

3. To compensate for a distinct lack of personality,  Herbert relies on the Grand Entrance
technique when he attends parties. His latest plan for appearing at a pool party is to arrive
by helicopter and then slide down a nylon rope as the helicopter hovers above poolside.
However, as the helicopter approaches its destination, the pilot tells Herbert that the rope
will break if the tension exceeds 300 N. Herbert, whose mass is 61.2 kg, realizes that
the rope won't hold him unless he slides down with an appropriate acceleration. What
must his acceleration be if the rope is not to break and ruin the whole effect?

4. A student has to escape from his girlfriend's dormitory through a window that is 15.0 m
above the ground. He has a 24-m rope, but it will break when the tension exceeds 360 N,
and the student weighs 600 N. The student will be injured if he hits the ground with a speed
greater than 8 m/s. (a) Show that he cannot safely slide down the rope. (b) Find a strategy
using the rope that will permit the student to reach the ground safely.

5. A rifle bullet of mass 9 g starts from rest and exits from the 0.6-m barrel at 1200 m/s.
Find the force exerted on the bullet, assuming it to be constant, while the bullet is in the barrel.

6. Abullet ofmass1.8×10--3kgmovingat 500 m/s Impacts with a large fixed block of wood and
travels 6 cm before coming to rest. Assuming that the deceleration of the bullet is constant,
find the force exerted by the wood on the bullet.

7. A 1000-kg load is being moved by a crane. Find the tension in the cable that supports
the load as (a) it is accelerated upward at 2 m/s2 , (b) it is lifted at constant speed, and
(c) it moves upward with speeddecreasing by 2 m/s each second.

8. A horse-drawn coach is decelerating at 3.0 m/s2  while moving in a straight line. A lamp
of mass 0.844 kg is hanging from the ceiling of the coach on a string 0.6 m long. The angle
that the string makes with the vertical is

(a) 8.5° toward the front of the coach.

(b) 17° toward the front of the coach.

(c) 17° toward the back of the coach.

(d) 2.5° toward the front of the coach.

(e) 0° or straight down.

9. A horizontal force of 100 N pushes a 12-kg block up a frictionless incline that makes an angle
of 25° with the horizontal. ( a) What is the normal force that the incline exerts on the block?
(b) What is the acceleration of the block?

10. A man stands on a scale in an elevator that has an upward acceleration a. The scale reads 960 N.

When he picks up a 20-kg box, the scale reads 1200 N. Find the mass of the man, his weight, and the

acceleration a.

11. A heavy rope of length 5m and mass 4kg lies on a frictionless horizontal table. One end is attached

to a 6-kg block. At the other end of the rope, a constant horizontal force of 100 N is applied. (a) What

is the acceleration of the system? (b) Give the tension in the rope as a function of position along the rope.

12. The acceleration of gravity g can be determined by measuring the time t it takes for a mass m2 in an

Atwood's machine to fall a distance L, starting from rest. (a) Find an expression for g in terms of m1 , m2 ,

L, and t. (b) Show that if there is a small error in the time measurement dt, it will lead to an error in the

determination of g by an amount dg given by dg/g = -2dt/t. If L=3m and m1 is 1kg, find the value of m2

such that g can be measured with an accuracy of ±5% with a time measurement that is accurate to 0.1 s.

Assume that the only significant uncertainty in the measurement is the time of fall. (paling susah)

13. A simple accelerometer can be made by suspending a small object from a string
attached to a fixed point on an accelerating object to the ceiling of a passenger car, for
example. When there is an acceleration, the object will deflect and the string will make some
angle with the vertical. (a) How is the direction in which the suspended object deflects related to
the direction of the acceleration? (b) Show that the acceleration a is related to the angle
θ that the string makes by a = g tan θ ; (c) Suppose the accelerometer is attached to
the ceiling of an automobile that brakes to rest from 50 km/h in a distance of 60 m.
What angle will the accelerometer make? Will the object swing forward or backward?

14. Joe and Sal are in a rollerbladers' club that is building a ramp to reach ne w levels of extremeness.

The ramp is to be a simple incline, so that after coasting horizontally, a skater will ride up the slope at

some angle θ. Sal suggests making the slope as steep as possible to maximize the height that will be

reached. Joe whips out a pencil and paper to prove to Sal that, if the surfaces are smooth,
the height reached is independent of the angle of the slope. Sal acknowledges that even though
Joe is being smug and obnoxious, his argument is sound. Show Joe's proof.

15.  A car traveling 90 km/h crashes into the rear end of an unoccupied stalled vehicle. Fortunately,
the driver is wearing a seat belt. Using reasonable values for the mass of the driver and the
stopping distance,estimate the force (assuming it to be constant) exerted on the driver by the seat belt.

16. Find the normal force and the tangential force exerted by the road on the wheels of your bicycle ( a)

as you climb an 8% grade at constant speed, (b) as you descend the 8% grade at constant speed. (An 8%

grade means that the angle of inclination θ is given by tan θ = 0.08). (paling susah )