A particle is thrown vertically upward. When it reaches the highest point, it has ______.
a downward acceleration
The correct answer is a downward acceleration.
Throughout its entire flight, neglecting air resistance, the only force acting on the particle is gravity. Gravity acts downwards, causing a constant downward acceleration equal to \(g\) (approximately 9.8 m/s²). This acceleration remains constant regardless of the particle's velocity or whether it's moving upwards or downwards.
Let's examine why the other options are incorrect:
- An upward acceleration: This would require a net upward force, which is not present in this scenario.
- A downward velocity: At the highest point, the particle momentarily stops before changing direction. Its velocity is zero at this instant.
- A horizontal velocity: The particle is thrown vertically; therefore, it has no horizontal motion.
Therefore, even at its highest point where the instantaneous velocity is zero, the particle continues to experience a constant downward acceleration due to the force of gravity.
Similar Questions
Select the option that is true regarding the following two statements labelled Assertion (A) and Reason (R).
(A): An object slips less on a rough surface than a smooth surface.
(R): When a surface is rough, frictional force increases.
Important Questions from Common forces in mechanics
Which of the following is NOT true about Frictional force?
A. Friction is the force which opposes the relative motion of two surfaces in contact.
B. The force of friction that acts when a body is moving (sliding) on a surface is called sliding friction.
C. Friction in machines wastes energy and also causes wear and tear.
D. Rolling friction is much more than sliding friction, the use of ball bearings in a machine considerably reduces friction.
Which of the following is a wrong example of friction?
Which one of the following statements about friction is incorrect?
- An electric lift with a maximum load of $2000\text{ kg}$ (lift + passengers) starts from rest and accelerates upwards at $0.2\text{ ms}^{-2}$. The frictional force opposing the motion is $3000\text{ N}$. The instantaneous power delivered by the motor when the lift reaches a speed of $1.5\text{ ms}^{-1}$ is:
(Assume $g = 10\text{ ms}^{-2}$) When a wheel is rolling on a level road, the direction of frictional force between the wheel and road is in:
