Never give your dog any medication unless your Vet tells you that it's okay. Some human medications can be given to dogs but can be lethal in the wrong doses.
Baby aspirin or aspirin is much safer for dogs than Motrin. Some dogs can tolerate Motrin while others cannot. Ask your vet for advice and correct dosage.
No. You should not give your dog any type of prescription or nonprescription medication. While small doses may seem safe, you never know what type of reaction your dog will have to the ingredients. There are medications available that are similar to Motrin that are made specifically for dogs. Always ask your vet first.