An object moving at a constant velocity requires a constant net force to maintain that motion.
Correct Answer
False
An object moving at a constant velocity has zero acceleration, and therefore, according to Newton's second law, the net force acting on it must be zero.
Question 2
The work done by a conservative force on an object moving between two points depends only on the initial and final positions, not on the path taken.
Correct Answer
True
This is the defining characteristic of a conservative force, such as gravity or an ideal spring force.
Question 3
If an object's velocity is zero at an instant, its acceleration must also be zero at that same instant.
Correct Answer
False
A ball thrown upwards momentarily has zero velocity at its peak, but its acceleration is still due to gravity (approximately 9.8 m/s^2 downwards).
Question 4
The magnitude of an object's average velocity can be greater than the magnitude of its average speed over the same time interval.
Correct Answer
False
Average velocity is the magnitude of displacement divided by time, while average speed is total distance traveled divided by time. Since the magnitude of displacement is always less than or equal to the total distance, the magnitude of average velocity can never be greater than average speed.
Question 5
The coefficient of static friction is generally greater than or equal to the coefficient of kinetic friction for the same pair of surfaces.
Correct Answer
True
It typically requires more force to initiate motion (overcome static friction) than to maintain motion at a constant speed (overcome kinetic friction).
Question 6
When a ball is thrown upwards, the work done by gravity on the ball is positive as it rises.
Correct Answer
False
As the ball rises, its displacement is upwards, but the gravitational force is downwards. Since the force and displacement are in opposite directions, the work done by gravity is negative.
Question 7
An object moving in a circle at a constant speed has zero acceleration.
Correct Answer
False
Even at a constant speed, an object moving in a circle is continuously changing direction. This change in velocity direction means there is a centripetal acceleration directed towards the center of the circle.
Question 8
If an object has constant acceleration, its velocity must be changing linearly with time.
Correct Answer
True
By definition, constant acceleration means the rate of change of velocity is constant, which results in a linear relationship between velocity and time (v = v0 + at).
Question 9
For an object undergoing projectile motion, its horizontal velocity remains constant if air resistance is negligible.
Correct Answer
True
In projectile motion without air resistance, gravity acts only vertically. Therefore, there is no horizontal force and no horizontal acceleration, causing the horizontal velocity to remain constant.
Question 10
According to Newton's third law, the action and reaction forces always act on the same object.
Correct Answer
False
Action-reaction pairs always act on *different* objects. If they acted on the same object, they would cancel out and could not cause acceleration.
Question 11
In an elastic collision, both kinetic energy and momentum are conserved.
Correct Answer
True
By definition, an elastic collision is one in which both the total kinetic energy and the total momentum of the system are conserved.
Question 12
The centripetal force acting on an object in uniform circular motion does positive work on the object.
Correct Answer
False
The centripetal force is always perpendicular to the instantaneous velocity (and thus to the displacement) of the object. Therefore, the work done by the centripetal force is always zero.
Question 13
If two objects collide and stick together, the collision is necessarily perfectly inelastic, and all kinetic energy is lost.
Correct Answer
False
While a collision where objects stick together is perfectly inelastic, it means the maximum possible amount of kinetic energy is lost consistent with momentum conservation. However, some kinetic energy typically remains, unless the final velocity of the combined mass is zero.
Question 14
Power is the rate at which work is done or energy is transferred.
Correct Answer
True
Power is defined as work divided by time (P = W/t) or the rate at which energy is transferred or transformed.
Question 15
If a car is accelerating forward, the force it exerts on the road is greater than the force the road exerts on the car.
Correct Answer
False
By Newton's third law, the force the car exerts on the road and the force the road exerts on the car are an action-reaction pair and must be equal in magnitude.
Question 16
An object's kinetic energy can be negative if its velocity is in the negative direction.
Correct Answer
False
Kinetic energy is given by (1/2)mv^2. Since mass (m) is always positive and velocity squared (v^2) is always non-negative, kinetic energy can never be negative.
Question 17
For an object to maintain uniform circular motion, a net force directed towards the center of the circle is required.
Correct Answer
True
This net force is the centripetal force, which causes the centripetal acceleration necessary to continuously change the direction of the object's velocity.
Question 18
In an inelastic collision, total kinetic energy is not conserved, but total momentum is always conserved if no external forces act.
Correct Answer
True
Momentum is conserved in all types of collisions (elastic or inelastic) provided the net external force on the system is zero. Kinetic energy is only conserved in elastic collisions.
Question 19
Impulse is equal to the change in an object's momentum.
Correct Answer
True
This statement is the impulse-momentum theorem, J = Δp.
Question 20
For an object to be in static equilibrium, the net force acting on it must be zero, but the net torque can be non-zero.
Correct Answer
False
For static equilibrium, both the net force *and* the net torque acting on the object must be zero. A non-zero net torque would cause angular acceleration.
Question 21
Increasing the radius of a circular path while keeping the tangential speed constant will decrease the required centripetal force.
Correct Answer
True
Centripetal force is given by F_c = mv^2/r. If mass (m) and tangential speed (v) are constant, increasing the radius (r) will decrease the required centripetal force.
Question 22
The magnitude of the torque produced by a force depends on the magnitude of the force, the distance from the pivot to the point where the force is applied, and the angle between the force vector and the lever arm.
Correct Answer
True
Torque (τ) is defined as rFsin(θ), where r is the lever arm, F is the force, and θ is the angle between the lever arm and the force vector. All three factors influence the magnitude of the torque.