# Physics questions

1. A sledge loaded with bricks has a total mass of 17.5 kg and is pulled at constant speed by a
rope inclined at 20.9° above the horizontal. The sledge moves a distance of 19.4 m on a
horizontal surface. The coefficient of kinetic friction between the sledge and surface is 0.500.
(a) What is the tension in the rope?
N
(b) How much work is done by the rope on the sledge?
kJ
(c) What is the mechanical energy lost due to friction?
kJ

2. A mechanic pushes a 2.80 103­kg car from rest to a speed of v, doing 5,000 J of work in

the process. During this time, the car moves 29.0 m. Neglecting friction between car and road,
find each of the following.
(a) the speed v
m/s
(b) the horizontal force exerted on the car
N

3. Two blocks are connected by a light string that passes over two frictionless pulleys as in the
figure below. The block of mass m2 is attached to a spring of force constant k and m1 > m2. If
the system is released from rest, and the spring is initially not stretched or compressed, find
an expression for the maximum displacement d of m2. (Use any variable or symbol stated
above along with the following as necessary: g.)
d =

4. A block of mass m = 6.80 kg is released from rest from point

and slides on the

frictionless track shown in the figure below. (Assume ha = 8.00 m.)

(a) Determine the block’s speed at points
point

point

and

.

m/s
m/s

(b) Determine the net work done by the gravitational force on the block as it moves from
point

to point

.
J

5. The system shown in the figure below is used to lift an object of mass m = 51.5 kg. A

constant downward force of magnitude F is applied to the loose end of the rope such that the
hanging object moves upward at constant speed. Neglecting the masses of the rope and
pulleys, find the following.

(a) Find the required value of F.
N
(b) Find the tensions T1, T2, and T3. (T3 indicates the tension in the rope which attaches the
pulley to the ceiling.)
T1 =
T2 =
T3 =

N
N
N

(c) Find the work done by the applied force in raising the object a distance of 2.20 m.
J

6. A skier of mass 78 kg is pulled up a slope by a motor­driven cable.
(a) How much work is required to pull him 50 m up a 30° slope (assumed frictionless) at a
constant speed of 2.8 m/s?
J
(b) What power (expressed in hp) must a motor have to perform this task?
hp

7. A pitcher claims he can throw a 0.160­kg baseball with as much momentum as a 2.20­g
bullet moving with a speed of 1.50 103 m/s.
(a) What must the baseball’s speed be if the pitcher’s claim is valid?
m/s

(b) Which has greater kinetic energy, the ball or the bullet?
A. The ball has greater kinetic energy.

B. The bullet has greater kinetic energy.
C. Both have the same kinetic energy.

8. The force shown in the force vs. time diagram in the figure below acts on a 3.2­kg object.

(a) Find the impulse of the force.
N ? s
(b) Find the final velocity of the object if it is initially at rest.
m/s
(c) Find the final velocity of the object if it is initially moving along the x­axis with a
velocity of
?1.6 m/s.
m/s

9. A 70.0­kg person throws a 0.0470­kg snowball forward with a ground speed of 27.0 m/s. A
second person, with a mass of 59.0 kg, catches the snowball. Both people are on skates. The
first person is initially moving forward with a speed of 2.50 m/s, and the second person is
initially at rest. What are the velocities of the two people after the snowball is exchanged?
Disregard the friction between the skates and the ice.
thrower
catcher

m/s
m/s

10. A railroad car of mass 2.0 104 kg moving at 4.00 m/s collides and couples with two
coupled railroad cars, each of the same mass as the single car and moving in the same
direction at 1.20 m/s.
(a) What is the speed of the three coupled cars after the collision?
m/s
(b) How much kinetic energy is lost in the collision?
J

11. A bullet of mass m = 8.00 g is fired into a block of mass M = 240 g that is initially at rest at
the edge of a table of height h = 1.00 m (see figure below). The bullet remains in the block,
and after the impact the block lands d = 2.20 m from the bottom of the table. Determine the
initial speed of the bullet.
? m/s

12. Consider a frictionless track as shown in the figure below. A block of mass m1 = 4.15 kg is
released from
. It makes a head­on elastic collision at
with a block of
mass m2 = 11.5 kg that is initially at rest. Calculate the maximum height to which m1 rises after
the collision.
? m