Advertisements
Advertisements
प्रश्न
A person standing near the edge of the top of a building throws two balls A and B. the ball A is thrown vertically upward and B is thrown vertically downward with the same speed. The ball A hits the ground with a speed vA and the ball B this the ground with a speed vB. We have
पर्याय
vA > vB
vA < vB
vA = vB
the relation between vA and vB depends on height of the building above the ground.
उत्तर
vA = vB
Total energy of any particle = \[\frac{1}{2}m v^2 + mgh\]
Both the particles were at the same height and thrown with equal initial velocities, so their initial total energies are equal. By the law of conservation of energy, their final energies are equal.
At the ground, they are at the same height. So, their P.E. are also equal; this implies that their K.E. should also be equal. In other words, their final velocities are equal.
APPEARS IN
संबंधित प्रश्न
The following figure gives the x-t plot of a particle in one-dimensional motion. Three different equal intervals of time are shown. In which interval is the average speed greatest, and in which is it the least? Give the sign of average velocity for each interval.
When a particle moves with constant velocity, its average velocity, its instantaneous velocity and its speed are all equal. Comment on this statement.
A car travels at a speed of 60 km/hr due north and the other at a speed of 60 km/hr due east. Are the velocities equal? If no, which one is greater? If you find any of the questions irrelevant, explain.
A motor car is going due north at a speed of 50 km/h. It makes a 90° left turn without changing the speed. The change in the velocity of the car is about ______.
A person travelling on a straight line moves with a uniform velocity v1 for some time and with uniform velocity v2 for the next equal time. The average velocity v is given by
The range of a projectile fired at an angle of 15° is 50 m. If it is fired with the same speed at an angle of 45°, its range will be
Consider the motion of the tip of the minute hand of a clock. In one hour
(a) the displacement is zero
(b) the distance covered is zero
(c) the average speed is zero
(d) the average velocity is zero
Pick the correct statements:
(a) Average speed of a particle in a given time is never less than the magnitude of the average velocity.
(b) It is possible to have a situation in which
(d) The average velocity of a particle moving on a straight line is zero in a time interval. It is possible that the instantaneous velocity is never zero in the interval. (Infinite accelerations are not allowed).
The velocity of a particle is zero at t = 0.
(a) The acceleration at t = 0 must be zero.
(b) The acceleration at t = 0 may be zero.
(c) If the acceleration is zero from t = 0 to t = 10 s, the speed is also zero in this interval.
(d) If the speed is zero from t = 0 to t = 10 s the acceleration is also zero in this interval.
In figure shows the position of a particle moving on the X-axis as a function of time.
It is 260 km from Patna to Ranchi by air and 320 km by road. An aeroplane takes 30 minutes to go from Patna to Ranchi whereas a delux bus takes 8 hours. Find the average speed of the bus.
It is 260 km from Patna to Ranchi by air and 320 km by road. An aeroplane takes 30 minutes to go from Patna to Ranchi whereas a delux bus takes 8 hours. Find the average velocity of the plane.
It is 260 km from Patna to Ranchi by air and 320 km by road. An aeroplane takes 30 minutes to go from Patna to Ranchi whereas a delux bus takes 8 hours. Find the average velocity of the bus.
An athlete takes 2.0 s to reach his maximum speed of 18.0 km/h. What is the magnitude of this average acceleration.
In the following figure shows the graph of the x-coordinate of a particle going along the X-axis as a function of time. Find the average velocity during 0 to 10 s,
Among the four graphs (Figure), there is only one graph for which average velocity over the time intervel (0, T ) can vanish for a suitably chosen T. Which one is it?
