(English Medium) ICSE Class 9 - CISCE Question Bank Solutions for Physics

The unit of retardation is ____________

A body is moving vertically upwards. Its velocity changes at a constant rate from 50 m s⁻¹ to 20 m s⁻¹ in 3 s. What is its acceleration?

A toy car initially moving with uniform velocity of 18 km h^-1 comes to a stop in 2 s. Find the retardation of the car in S.I. units.

State the type of motion represented by the following sketches in Figures.

Give an example of each type of motion.

Figure shows the velocity-time graphs for two cars A and B moving in the same direction. Which car has greater acceleration? Give reasons to your answer.

The velocity-time graph for a uniformly retarded body is a straight line inclined to the time axis with an obtuse angle. How is retardation calculated from the velocity-time graph?

Draw a graph for acceleration against time for a uniformly accelerated motion. How can it be used to find the change in speed in a certain interval of time?

A body falls freely from a certain height. Show graphically the relation between the distance fallen and square of time. How will you determine g from this graph?

Figure given below shows a velocity-time graph for a car starting from rest. The graph has three parts AB, BC and CD.

(a) Is the magnitude of acceleration higher or lower than that of retardation ? Give a reason .
(b) Compare the magnitude of acceleration and retardation .

Figure given below shows a velocity-time graph for a car starting from rest. The graph has three parts AB, BC and CD.

Which part of graph shows motion with uniform
(a) velocity (b) acceleration (c) retardation ?

A bullet initially moving with a velocity 20 m/s strikes a target and comes to rest after penetrating a distance 10 cm into the target. Calculate the retardation caused by the target.

A train moving with a velocity of 20 ms⁻¹ is brought to rest by applying brakes in 5 s. Calculate the retardation.

A train starts from rest and accelerates uniformly at a rate of 2 m s⁻² for 10 s. It then maintains a constant speed for 200 s. The brakes are then applied and the train is uniformly retarded and comes to rest in 50 s. Find

1. The maximum velocity reached,
2. The retardation in the last 50 s,
3. The total distance travelled,
4. The average velocity of the train.

A space craft flying in a straight course with velocity of 75 km s^-1 fires its rocket motors for 6.0 s. At the end of this time its speed is 120 km s^-1 in the same direction.

Find

(i) The space craft's average acceleration while the motors were firing

(ii) The distance travelled by the space craft in the first 10 s after the rocket motors were started, the motors being in action for only 6 s.

A car travels with uniform velocity of 25 m s^-1 for 5 s. The brakes are then applied and the car is uniformly retarded and comes to rest in further 10 s. Find:

1. The distance which the car travels before the brakes are applied,
2. Retardation and
3. The distance travelled by car after applying the brakes.

A vehicle is accelerating on a straight road. Its velocity at any instant is 30 km/h. After 2 s, it is 33.6 km/h, and after further 2 s, it is 37.2 km/h. Find the acceleration of the vehicle in m s^-2. Is the acceleration uniform?

A body of volume V and density ρ is kept completely immersed in a liquid of density ρ_L. If g is the acceleration due to gravity, then write expressions for the following:

(i) The weight of the body, (ii) The upthrust on the body,

(iii) The apparent weight of the body in liquid, (iv) The loss in weight of the body. 

A sphere of iron and another sphere of wood of the same radius are held under water. Compare the upthrust on the two spheres.

[Hint: Both have equal volume inside the water].

A sphere of iron and another of wood, both of same radius are placed on the surface of water. State which of the two will sink? Give a reason for your answer. 

How does the density of material of a body determine whether it will float or sink in water?