Numerical Problems | Physics 9th | Chapter 3 Dynamics | KPK Textbook Book Board Peshawar | SLO Base

Encircle the best possible option.
A 30kg object is supported from rope, such that tension in the rope is equal to its weight. The weight of the object is
(a) 30kg (b) 30N (c) 294N (d) 9.8N/kg
Force needed to produce an acceleration of 10〖ms〗^(-2) in a ball of mass 0.5kg is
(a) 20N (b) 10.5N (c) 9.5N (d) 5N
Ball A collide with ball B which is at rest, after the collision which of the following condition is not possible
(a) Ball A comes to rest and ball B start moving (b) Both balls move in same direction
(c) Both balls move in opposite directions (d) Both balls are at rest
What is the mass of a car that is traveling with a velocity of 20〖ms〗^(-1) [W] and a momentum of 22000kg〖ms〗^(-1) [W]
(a) 440000kg (b) 21980kg (c) 22020kg (c) 1100kg
An object at earth and taken to moon should have
(a) less mass/less weight (b) same mass/same weight
(c) same mass/less weight (d) less mass/same weight
The unit of coefficient of friction is
(a) N (b) kg (c) μ (d) it has not units
The centripetal acceleration for an object of mass 1kg moving with 6〖ms〗^(-1) in a circle of radius 3m is
(a) 18〖ms〗^(-2) (b) 12〖ms〗^(-2) (c) 10〖ms〗^(-2) (d) 2〖ms〗^(-2)
How many times the centripetal force will increase if the mass of a body moving with uniform speed in a circle is doubled?
(a) six time s (b) two times (c) four times (d) eight times
Which of the following forces can act as a centripetal force
(a) tension (b) friction (c) gravitational force (d) all of these
An empty suitcase is placed in the middle of bus on its floor traveling at high speed. When the bus take brake suddenly, the suitcase slide
(a) backwards (b) forward (c) jumps up (d) remains in place
In Newton’s third law the action reaction pair does not neutralize each other, because they
(a) act on same body (b) act on different bodies (c) act on third body (d) produce friction
Give a brief response to the following questions
Why does dust fly off, when a hanging carpet is beaten with a stick?
If your hands are wet and no towel is handy, you can remove some of the excess water by shaking them. Why does this work?
Why a balloon filled with air move forward, when its air is released?
Why does a hose pipe tend to move, backward when the fireman directs a powerful stream of water towards fire?
Your car is stuck in wet mud. Some students on their way to class see your predicament and help out by sitting on the trunk of your car to increase its traction. Why does this help?
How does frication help you walk? Is it kinetic friction or static friction?
The parking brake on a car causes the rear wheels to lock up. What would be the likely consequence of applying the parking brake in a car what is in rapid motion?
Why is the surface of a conveyor belt made rough?
Why does a boatman tie his boat his pillar before allowing the passengers to step on the river bank?
In uniform circular motion, is the velocity constant? Is the acceleration constant? Explain.
You tie a brick to the end of a rope and whirl the brick around you in a horizontal circle. Describe the path of the brick after you suddenly let go of the rope.
Why is the posted speed for a turn lower than the speed limit on most highways?
Q. Solve the following numerical questions.
1580kg car is traveling with a speed of 15.0〖ms〗^(-1). What is the magnitude of the horizontal net force that is required to bring the car to a halt in a distance of 50.0m?
A bullet of mass 10g is fired with a rifle. The bullet takes 0.003s to move through barrel and leaves with a velocity of 300〖ms〗^(-1). What is the force exerted on the bullet by the rifle?
A 2200kg vehicle traveling at 94〖kmh〗^(-1) (26〖ms〗^(-1)) can be stopped in 21s by gently applying the brakes. It can be stopped in 3.8s if the driver slams on the brakes. What average force is exerted on the vehicle if both of these stops?
You want to move a 500N crate across a level floor. To start the crate moving, you have to pull with a 230N horizontal force. Once the crate “breaks loose” and starts to move, you can keep it moving at constant velocity with only 200N. What are the co-efficient of static and kinetic friction?
Two bodies of masses 3kg and 5kg are tied to string which is passed over a pulley. If the pulley has no friction, find the acceleration of the bodies and tension in the string.
Determine the magnitude of the centripetal force exerted by the rim of a car’s wheel on a 45.0kg tyre. The tyre has a 0.480m radius and is rotating at a speed of 30〖ms〗^(-1).
A motorcyclist is moving along a circular wooden track of a circus (death well) of radius 5m at a speed of 10〖ms〗^(-1). If the total mass of motorcycle and the rider is 150kg find the magnitude of the centripetal force acting on him?
A car of mass 1000kg is running on a circular motor way interchange near Swabi with a velocity of 80〖ms〗^(-1) the radius of the circular motorway interchange is 800m. How much centripetal force is required?