Advertisements
Advertisements
प्रश्न
If the energy of a ball falling from a height of 10 metres is reduced by 40%, how high will it rebound?
उत्तर
Given:
Height (h1) = 10 m
PE2 = PE1 - PE1 of 40%
Find: Height (h2)
Formula: P.E. = mgh
Calculations:
PE1 = mgh1 ...(i)
PE2 = mgh2 ...(ii)
PE2 = PE1 of 60%
Dividing equation (ii) by (i).
`"PE"_2/"PE"_1 = ("mgh"_2)/("mgh"_1)`
`(60%"PE"_1)/("PE"_1) = "h"_2/10`
`60/100 = "h"_2/10`
`"h"_2 = (60 xx 10)/100`
h2 = 6 m
∴ The ball will bounce up to a height of 6 m when it hits the ground.
APPEARS IN
संबंधित प्रश्न
Write true or false of the following statement.
A gum bottle lying on a table has no energy.
Write true or false of the following statement.
In an electric fan, electrical energy changes into the mechanical energy.
Fill in the blank
An electric fan converts electrical energy into ______ energy.
Fill in the blank
Cooking gas converts _______ energy into heat energy.
Fill in the blank
The ability to do work is called ______
Match the following columns
| COLUMN A | COLUMN B |
| 1. Running water | 1. heat energy |
| 2. Burning | 2. vibrations |
| 3.Energy | 3.atom bomb |
| 4.Sound energy | 4.kinetic energy |
| 5.Nuclear energy | 5.joule |
State the unit of energy and define it.
What is potential energy ? State its unit.
Name the commercial unit of measurement of energy.
Name the quantity whose unit is :
(a) kilowatt
(b) kilowatt-hour
A cell converts one form of energy into another form. Name the two forms.
Derive the relation between commercial unit of energy (kWh) and SI unit of energy (joule).
The commercial unit of energy is :
- Take two aluminium channels of different lengths.
- Place the lower ends of the channels on the floor and hold their upper ends at the same height.
- Now take two balls of the same size and weight and release them from the top end of the channels. They will roll down and cover the same distance.
- At the moment of releasing the balls, which energy do the balls have?
- As the balls roll down which energy is converted into which other form of energy?
- Why do the balls cover the same distance on rolling down?
Note: The question is wrong. It should be "Why do the balls cover the same distance after rolling down"? - What is the form of the eventual total energy of the balls?
- Which law related to energy does the above activity demonstrate? Explain.
Can you tell?
When can we say that displacement has taken place?
Which one of the following requires wind energy?
Find out the form of energy possessed by the following thing.
A rock on the top of a hill
What energy transfer happen in a car engine?
Define kilowatt hour.
