Download Set 1

Set 3. Force and Motion
Force. Resultant (net) force. The principle of superposition for forces. Force units. Newton's
First Law. Newton's Second Law. Newton's Third Law. The gravitational force. Friction.
Tension. Centripetal force.
Ex.1
A block S of mass M = 3.3 kg is connected to a block H of mass m = 2.1 kg by a cord that wraps
over a pulley. The cord and pulley have negligible masses compared to the blocks. The block S
accelerates along a horizontal frictionless surface as the block H falls.
Find:
1. the acceleration of the block S,
2. the acceleration of the block H,
3. the tension in the cord T.
Ex.2
There are two blocks of masses m = 1.3 kg and m = 2.8 kg connected by a cord that passes over a
1
2
pulley. The cord and pulley have negligible masses compared to the blocks. The pulley is
frictionless.
Find:
1. the acceleration of the block m ,
2. the acceleration of the block m1 ,
2
3. the tension in the cord.
Ex. 3
= 3.7 kg is lying on a frictionless plane inclined at angle α=30° and it is
A block of mass m
1
connecting by a cord over massless, frictionless pulley to a second block of mass m = 2.30 kg
2
hanging vertically.
Find:
1. the acceleration of the block m ,
1
2. the acceleration of the block m ,
2
3. the tension in the cord.
Ex. 4
There are three blocks of masses m = 12 kg, m = 24 kg, m = 31 kg connected with each
1
2
3
other by a cord. They are pulled to the right on a horizontal frictionless table by a force of
magnitude T = 65N.
3
Find:
1. the system acceleration of the block m ,
1
2. the tension T ,
2
3. the tension T .
3
Ex. 5
A sphere of mass 3x10-4 kg is suspended on a cord. A steady horizontal breeze pushes the
sphere so that the cord makes a constant angle of 37° with the vertical:
Find:
1. the force that pushes the sphere,
2. the tension in the cord.
Ex. 6
An elevator cab with a man inside have a combined mass of 1600 kg. Find the tension in the
supporting cable when the cab originally moving downward at 12 m/s, is brought to rest with
constant acceleration in a distance of 42 m.
Ex. 7
2
A lamp hangs vertically from a cord in a descending elevator that decelerates at 2.4 m/s .
Find:
1. the lamp mass if the tension in the cord is 89 N,
2. the cord tension when the elevator ascends with an upward acceleration of 2.4 m/s.
Ex. 8
An elevator cab that weighs 27.8 kN moves upward. What is the tension in the cable if the cab
speed is
2
1. increasing at a rate of 1.22 m/s ,
2
2. decreasing at a rate of 1.22 m/s .
Ex. 9
A roller-coaster car has a mass of 1200 kg when fully loaded with passengers. As the car passes
over the top of a circular hill of radius 18 m, its speed is not changing. At the top of the hill what
are the magnitude and direction (up or down) of the normal force F acting on the car from the
N
track if the car speed is v =11 m/s? What is the magnitude of F and its direction if the car speed is
1
N
v =14 m/s?
2
Ex. 10
A car is driven at constant speed over a circular hill and then into a circular valley with the same
radius. At the top of the hill the normal force acting on the driver from the car seat is 0 N. The
driver mass is 70 kg. What is the magnitude of the normal force acting on the driver from the
seat when the car passes through the bottom of the valley?
Ex. 11
A high-speed railway car goes around a flat, horizontal circle of radius 470 m at a constant
speed. The magnitudes of the horizontal and vertical components of the force of the car on a
passenger are 210 N and 500 N, respectively. What is the magnitude of the net force (of all the
forces) on the passenger? What is the speed of the car?