Could be many things, but your rotors are probably warped, or cracked, or about to go. Not something you want to let slide, especially if you have kids in the car. Just picture them all the sudden not working at all, or locking up unexpectedly... what are you gonna do??
While driving, apply the brakes gently for a short distance, as you maintain your speed.
The most likely cause is a warped rotor. It can also be other things so have you brakes and suspension inspected.
Your front end is probably out of alignment. Have it checked at a mechanic.
i had one go bad an it started out with a slight rattle when the engine was running at idle. You cannot notice the noise at speed . Took the truck to a muffler shop and had it inspected and replaced. you could shake the cat and hear the baffle rattle inside
Could be,Tire(s) out of balance, A worn tie-rod end (s),
Yes, the parking brakes can be used to stop the vehicle in emergency. But remember that, in most of the vehicles parking brakes apply only to one pair of wheels, so if the vehicle is in high speed, one has to apply them carefully and save the vehicle from skidding.
the brakes affect the speed
That means person inside car is either too heavy or something like a toy is caught in engine
High speed vibration is often an indication of a wheel that is out of balance or a bent rim. It can also be a bent driveshaft or bad U-joint. Vibration when you brake at high speed is almost always a warped rotor on the disk brakes.
Using brakes slows your speed.
suppose when we apply brakes to a car in motion then the speed of the car decreases which means the acceleration is backwards but the car is still running in the forward direction
Since you didn't specify WHEN it shakes (high speed, when using the brakes, low speed???) here are a couple possibilities:wheel balance,worn suspension,worn steering linkage,bent wheel,defective tire.And if it only occurs when you use the brakes, it could even be a faulty rotor even if it IS supposed to be new.