An example is when u rub your pen on your hair hard that is friction
Answer:
Gamma rays are mostly used in the radiotherapy/ radiooncology to treat cancer. They can also be used to spot tumours. Gamma rays can kill living cells and damage malignant tumor
Answer:
1. Recollapsing universe
2. Critical universe
3. Coasting universe
Explanation:
Recollapsing universe has dark matter density greater than critical density. While critical universe has its matter density equal to the critical sensity. Coasting universe on the other hand has much smaller matter density compared to critical density.
Note that the critical density is approximately 10^-20 grams/cm3