1980 年

A ball is dropped from a height $h$ above the ground. Each time it hits the ground, one-half of the original kinetic energy is lost. How high will the ball rise above the ground after the second impact ?

Two blocks $A$ and $B$ of masses $m_1$ and $m_2$ are connected by a light spring on a horizontal frictionless table. The spring is stretched by moving the blocks apart. What is the ratio of the acceleration of $A$ to that of $B$ at the moment when they are released ?

An object is resting on a rough plane inclined at an angle $\theta$ to the horizontal. As $\theta$ gradually increases, the frictional force acting on the object before sliding occurs is directly proportional to

An object is thrown vertically upwards with initial speed $u$. Which of the following graphs represents the variation of its kinetic energy $E_k$ with time $t$ ?

Two objects $P$ and $Q$ of mass $2$ kg and $3$ kg respectively have the same momentum. They are then subjected to the same constant resisting force and gradually brought to rest. What is the ratio of the stopping distance of $P$ to that of $Q$ ?

A horizontal force $F$ is applied to a block of mass $M$ on a rough horizontal surface. The acceleration of the block is $a$. If the force is changed to $2F$ and the frictional force remains unchanged, then the acceleration of the block will be

In the figure, $X$ and $Y$ are blocks of mass $1$ kg and $2$ kg respectively. $S$ is a spring balance of negligible mass and $P$ is a smooth pulley fixed at the top of two smooth inclined planes. What is the reading of $S$ when $X$ is held stationary by an external force ?

A body is dropped from rest down a cliff on a planet $X$. After falling for $1$ s, it is $4$ m below the starting point. How far below the starting point will it be after a further $4$ s ?

A spring balance suspended from the ceiling of a lift registers the weight of a $20$ kg body as $150$ N. The lift is probably